WBP SI Prelims Science Previous Year Questions with Answers

Correct Answer: (C) Tor

Explanation

The Tor browser (The Onion Router) sends a user’s traffic through several volunteer relays wrapped in layers of encryption, which hides the identity of the user and allows access to .onion sites on the dark web. Chrome is an ordinary browser, and iOS and Linux are operating systems.

Exam Facts

• Tor stands for The Onion Router and uses onion routing, where data passes through at least three relays, each removing one layer of encryption.
• Onion routing was first developed in the mid-1990s at the US Naval Research Laboratory, and the non-profit Tor Project maintains the browser today.
• Dark web sites use the .onion address and cannot be opened by normal search engines.
• The dark web is a small, deliberately hidden part of the deep web, which means all web content not indexed by search engines (such as bank accounts and email inboxes).
• Option (A) Google Chrome is a normal web browser of Google (launched in 2008) and does not open .onion sites by default.
• Option (B) iOS is the mobile operating system of Apple’s iPhone, not a browser.
• Option (D) Linux is a free, open-source operating system kernel created by Linus Torvalds in 1991.
• A VPN (Virtual Private Network) also hides an IP address, but it does not give access to the dark web by itself.
• Cyber crime in India is dealt with under the Information Technology Act, 2000.
• CERT-In (Indian Computer Emergency Response Team) is the national agency for cyber-security incidents.

Correct Answer: (C) Pancreas

Explanation

The pancreas is called a mixed gland because it works both as an exocrine gland (it sends digestive pancreatic juice through the pancreatic duct to the small intestine) and as an endocrine gland (its islets of Langerhans release insulin and glucagon directly into the blood).

Exam Facts

• The islets of Langerhans contain alpha cells (glucagon), beta cells (insulin) and delta cells (somatostatin).
• Insulin lowers blood sugar, and its shortage causes diabetes mellitus; insulin was discovered by Banting and Best in 1921.
• Pancreatic juice contains the enzymes amylase, trypsin and lipase, which digest starch, proteins and fats.
• The gonads (testes and ovaries) are also mixed glands because they make both hormones and gametes.
• Option (A) Thyroid is a purely endocrine gland that makes thyroxine; a shortage of iodine causes goitre.
• Option (B) Liver is the largest gland of the body and an exocrine gland that makes bile.
• Option (D) Pituitary is the master gland, a purely endocrine gland situated at the base of the brain.
• Exocrine glands (such as salivary glands) have ducts, while endocrine glands are ductless.
• The adrenal glands (adrenaline) and the thymus are other important endocrine glands.
• Hormones are chemical messengers carried by the blood; the term was coined by Starling.

Correct Answer: (A) −273·15°C

Explanation

Absolute zero is the lowest possible temperature, at which the motion of particles is minimum. It is 0 K on the Kelvin scale, which equals −273.15°C on the Celsius scale.

Exam Facts

• The Kelvin scale is the SI scale of temperature and is named after Lord Kelvin; its unit is the kelvin (K), not the degree.
• The conversion is K = °C + 273.15, so 0°C = 273.15 K.
• Absolute zero is also −459.67°F on the Fahrenheit scale.
• By the third law of thermodynamics absolute zero can be approached but never reached.
• Near absolute zero a Bose-Einstein condensate is formed, and some metals become superconductors.
• Option (B) −237.15°C is a wrong figure made by swapping the digits of 273.15.
• Option (C) −373.15°C is wrong; 373.15 K (not −373.15°C) is the boiling point of water.
• Option (D) 0°C is the freezing point of water (273.15 K).
• On the Celsius scale water freezes at 0°C and boils at 100°C at normal pressure.
• Cryogenics is the study of very low temperatures; liquid helium boils at about 4.2 K.

Correct Answer: (C) Mitosis

Explanation

Amoeba reproduces asexually by binary fission: its nucleus first divides by mitosis (karyokinesis) and then the cytoplasm divides (cytokinesis), giving two identical daughter amoebae. Flag: some older books call this division amitosis, and option (B) ‘Micosis’ is not a real term, so the question is loosely worded; mitosis is the accepted modern answer.

Exam Facts

• Mitosis is an equational division in which a cell makes two daughter cells with the same chromosome number as the parent.
• Binary fission is also the method of bacteria, Paramecium and Euglena.
• Under unfavourable conditions Amoeba forms a cyst (encystation) and later divides by multiple fission (sporulation).
• Amitosis is the direct division of the nucleus without spindle or visible chromosomes, as in some protozoan nuclei and degenerating cells; this is the reason why option (A) is arguable.
• Meiosis (option D) is the reduction division that makes gametes with half the chromosome number.
• Option (B) Micosis has no meaning; it looks like a misprint of mitosis or meiosis.
• The stages of mitosis are prophase, metaphase, anaphase and telophase.
• Amoeba moves with pseudopodia and takes food by phagocytosis.
• Amoebic dysentery is caused by the parasite Entamoeba histolytica.
• The cell theory was proposed by Schleiden and Schwann, and Virchow added that new cells arise from pre-existing cells.

Correct Answer: (C) Influenza

Explanation

Influenza (flu) is a viral disease caused by the influenza virus, whereas typhoid, pneumonia and diphtheria are mainly bacterial diseases.

Exam Facts

• Typhoid is caused by the bacterium Salmonella typhi and is diagnosed by the Widal test.
• Pneumonia is mostly caused by the bacterium Streptococcus pneumoniae (it can also be viral).
• Diphtheria is caused by Corynebacterium diphtheriae and is prevented by the DPT vaccine.
• Influenza is caused by an RNA virus of the orthomyxovirus family and spreads through droplets.
• The 1918 pandemic called the Spanish flu was an influenza pandemic.
• Antibiotics such as penicillin work against bacteria but not against viruses.
• Other bacterial diseases are cholera (Vibrio cholerae), tuberculosis (Mycobacterium tuberculosis), tetanus and plague.
• Other viral diseases are polio, measles, mumps, dengue, rabies and COVID-19.
• Robert Koch is the father of bacteriology, and Louis Pasteur developed the germ theory and vaccines.
• Vaccines exist for typhoid, diphtheria and influenza, but treatment of bacterial diseases needs antibiotics.

Correct Answer: (A) Artery

Explanation

Blood does not clot inside healthy vessels; among the options the artery is the vessel in which blood flows fast under high pressure, so clots do not form easily, and it is taken as the answer. Flag: the question is ambiguous, because clots can form in any vessel when it is injured or the blood slows down.

Exam Facts

• Blood clotting (coagulation) converts soluble fibrinogen into insoluble fibrin with the help of the enzyme thrombin.
• Platelets (thrombocytes), calcium ions and vitamin K are essential for clotting.
• Heparin, made in the body, prevents clotting inside the vessels.
• Arteries carry blood away from the heart at high pressure and have thick elastic walls.
• Veins carry blood towards the heart at low pressure and have valves; slow flow can lead to clots such as deep vein thrombosis.
• Capillaries are the thinnest vessels, and blood clots at a wound where a capillary is cut (option B).
• A clot that forms inside a blood vessel is called a thrombus, and the condition is thrombosis.
• Haemophilia is a hereditary disease in which blood does not clot normally.
• The brain (option C) is an organ and not a vessel, and a blood clot there causes a stroke.
• The normal clotting time of human blood is about 3 to 8 minutes.

Correct Answer: (A) chances of storm

Explanation

A barometer measures atmospheric pressure. A sudden and rapid fall of the mercury level shows a fast drop in pressure, which warns of a storm or cyclone, while a slow fall indicates rain.

Exam Facts

• The mercury barometer was invented by Torricelli in 1643.
• Normal sea-level pressure supports a mercury column of 760 mm (76 cm).
• A slow fall of the mercury shows rain (option D), but a rapid fall shows a storm.
• A steady rise of the mercury shows clear and fair weather, so options (B) and (C) are linked with a rising barometer.
• A cyclone is a low-pressure system with winds circling inwards.
• The aneroid barometer works without liquid and is used in aircraft as an altimeter.
• Pressure is measured in millibar or hectopascal (hPa); 1 atmosphere is 1013.25 mb.
• Pressure decreases with height, by about 1 mb for every 10 m near the ground.
• The instrument for measuring humidity is the hygrometer, and for rainfall the rain gauge.
• Winds blow from high pressure to low pressure.

Correct Answer: (D) Neptune

Explanation

Neptune is the eighth full planet of the solar system and is not a dwarf planet. Pluto, Ceres and Eris are dwarf planets.

Exam Facts

• The IAU (International Astronomical Union) defined a planet and a dwarf planet in August 2006 at Prague; Pluto was reclassified as a dwarf planet.
• A dwarf planet orbits the Sun and is round, but it has not cleared its orbit of other objects.
• The five recognised dwarf planets are Pluto, Eris, Haumea, Makemake and Ceres.
• Ceres lies in the asteroid belt between Mars and Jupiter and was discovered by Giuseppe Piazzi in 1801.
• Pluto was discovered by Clyde Tombaugh in 1930, and New Horizons flew past it in 2015.
• Eris was discovered in 2005 by Mike Brown and his team; it is slightly more massive than Pluto.
• Neptune was discovered in 1846 (found by Galle after the calculations of Le Verrier and Adams).
• The eight planets in order from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
• Neptune is the farthest planet from the Sun and has a moon called Triton.
• The Dawn spacecraft of NASA orbited Ceres.

Correct Answer: (A) Pressure

Explanation

The torr is a unit of pressure. One torr is 1/760 of a standard atmosphere, which is about 133.3 pascal (nearly 1 mm of mercury).

Exam Facts

• The unit is named after the Italian scientist Evangelista Torricelli, the inventor of the mercury barometer.
• 1 atmosphere = 760 torr = 760 mm Hg = 101325 Pa.
• The SI unit of pressure is the pascal (Pa), which equals one newton per square metre.
• Other units of pressure are the bar, millibar and atmosphere.
• Option (B) Momentum has the SI unit kg m/s (or newton second).
• Option (C) Work has the SI unit joule, where 1 J = 1 N m.
• Option (D) Force has the SI unit newton, and the CGS unit is the dyne.
• Pressure = force / area, so a smaller area gives a larger pressure for the same force.
• A sphygmomanometer measures blood pressure in mm Hg.
• Torricelli’s experiment of 1643 showed that a vacuum could exist above the mercury column.

Correct Answer: (D) Phishing

Explanation

Phishing is a cyber crime in which a fraudster uses fake emails, websites or duplicate applications that look genuine, to trick users into revealing passwords, OTPs or card details.

Exam Facts

• Phishing usually pretends to come from a bank, a company or a government office.
• Vishing is phishing by a voice call, and smishing is phishing by SMS.
• Option (A) Bullying (cyber bullying) means harassing or threatening a person online.
• Option (B) Stalking (cyber stalking) means repeatedly following or watching a person online.
• Option (C) E-bombing (mail bombing) means flooding an inbox with huge numbers of emails.
• Under the Information Technology Act, 2000, Section 66C deals with identity theft and Section 66D with cheating by personation using a computer.
• Two-factor authentication and never sharing an OTP are the best protections.
• A password should be long and mix letters, numbers and symbols.
• Malware, ransomware and spyware are different kinds of harmful software.
• India’s cyber crime complaints can be filed on the National Cyber Crime Reporting Portal (cybercrime.gov.in).

Correct Answer: (A) Methane Hydrate

Explanation

Fire ice is the popular name of methane hydrate, an ice-like solid in which methane gas is trapped inside a cage of water molecules. It burns when lit, which gives it the name.

Exam Facts

• Methane hydrate is a type of clathrate (gas hydrate) formed at low temperature and high pressure.
• It is found under the ocean floor and in permafrost regions.
• One cubic metre of methane hydrate can release about 160 cubic metres of methane gas.
• It is considered a possible future energy source, but it is hard to extract, and leaking methane is a greenhouse gas.
• Japan produced gas from methane hydrate from the Nankai Trough in 2013.
• India has gas hydrate deposits in the Krishna-Godavari basin and the Andaman area, studied under the National Gas Hydrate Programme.
• Methane (CH4) is the main component of natural gas and biogas, and it is the simplest alkane.
• Option (B) propene hydrate, (C) methylene hydrate and (D) ethane hydrate are not called fire ice.
• Dry ice is solid carbon dioxide, a different ‘ice’.
• CNG (compressed natural gas) is mainly methane and is used as a vehicle fuel.

Correct Answer: (A) Plant and Animal fossils

Explanation

Palaeontology is the branch of science that studies fossils, the preserved remains or impressions of ancient plants and animals, to understand the history and evolution of life on Earth.

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Correct Answer: (D) principle of inertia

Explanation

Newton’s first law says that a body remains at rest or in uniform motion in a straight line unless an external force acts on it. This tendency to resist change is called inertia, so the law is the principle (law) of inertia.

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Correct Answer: (B) all the four valence electrons are bonded to each carbon atom by covalent bonds.

Explanation

In diamond each carbon atom uses all four valence electrons to form four strong covalent bonds with four other carbon atoms in a rigid tetrahedral network. Breaking this network needs a great deal of energy, so diamond is the hardest natural substance.

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Correct Answer: (A) Darwin

Explanation

The theory of natural selection was given by Charles Darwin in his book On the Origin of Species (1859). It says that individuals with favourable variations survive and reproduce more, so the species evolves.

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Correct Answer: (C) Insulin

Explanation

Insulin is the hormone that lowers blood sugar. In diabetes mellitus the pancreas makes too little insulin (or the body cannot use it), so a diabetic patient needs insulin (or other drugs that control blood glucose).

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Correct Answer: (B) Methane

Explanation

Gobar gas (biogas) is made when bacteria break down cattle dung without air (anaerobic digestion). Its main constituent is methane (CH₄), about 55-65%, and this is what burns as fuel.

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Correct Answer: (C) Angstrom

Explanation

The angstrom (Å) is a unit of length, equal to 10⁻¹⁰ m, used for atomic sizes and wavelengths of light. The coulomb, siemens and ohm are all electrical units.

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Correct Answer: (C) Vitamin-A

Explanation

Cow’s milk contains the fat-soluble vitamin A (retinol, with carotene giving the creamy-yellow tint) along with the B-complex vitamins. The question is loosely worded, because milk is a rich source of both vitamin A (option C) and vitamin B (option A, especially B₂ and B₁₂); the usual textbook answer, kept here, is (C) Vitamin-A.

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Correct Answer: (B) Rhizobium

Explanation

Rhizobium is the best-known nitrogen-fixing bacterium; it lives in the root nodules of leguminous plants (pea, gram, beans) and converts atmospheric nitrogen into ammonia. Note that Azotobacter (option C) also fixes nitrogen, so two options are correct; the classic answer, (B) Rhizobium, is kept.

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Correct Answer: (C) Chloroplasts

Explanation

Chloroplasts contain the green pigment chlorophyll, which traps sunlight for photosynthesis, so the chloroplast is the suitable option. The wording is loose, because the pigment itself is chlorophyll and the chloroplast is the cell part that holds it.

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Correct Answer: (A) Force

Explanation

A vector quantity has both magnitude and direction. Force has a magnitude (in newtons) and a direction in which it acts, so it is a vector.

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Correct Answer: (B) the ultraviolet rays convert skin oil into vitamin-D.

Explanation

Sunlight contains ultraviolet (UV-B) rays, which change a cholesterol compound of the skin oil (7-dehydrocholesterol) into vitamin D₃, which is needed for strong bones.

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Correct Answer: (D) Nuclear Fusion

Explanation

The Sun gets its energy from nuclear fusion, in which hydrogen nuclei combine to form helium in its core at about 15 million K. A small part of the mass is converted to energy according to E = mc².

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Correct Answer: (A) Fungi

Explanation

Athlete’s foot (tinea pedis) is a skin infection of the feet, usually between the toes, caused by fungi called dermatophytes (such as Trichophyton). It spreads in warm, damp places like locker rooms.

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Correct Answer: (A) 332 m/sec

Explanation

Under normal conditions (about 0 °C) the speed of sound in air is about 332 m/s (in school books 330-332 m/s), so option (A) is correct.

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Correct Answer: (D) Newton’s Law

Explanation

A rocket works on Newton’s third law of motion (and the law of conservation of momentum): the hot gases are thrown backward at high speed, and the rocket gets an equal and opposite push forward.

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Correct Answer: (B) Silicon

Explanation

Commercial fertilisers supply the three major plant nutrients N, P and K (nitrogen, phosphorus and potassium). Silicon is not added, because soils are already full of silicates and it is not a major nutrient, so it is the least likely.

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Correct Answer: (D) Diamond

Explanation

Diamond has the highest density, about 3.5 g/cm³, because its carbon atoms are packed in a compact three-dimensional tetrahedral lattice.

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Correct Answer: (D) Radon

Explanation

Helium, argon and xenon are stable noble gases that form part of the air, but radon is a radioactive gas of very short life, found only in negligible traces from uranium decay, and so it is not counted as a constituent. Strictly, traces of radon do exist in air, which is why this is the expected answer rather than a perfect one.

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Correct Answer: (B) Gamma

Explanation

In radioactivity alpha and beta are particles and gamma is a high-energy electromagnetic radiation (a ray) with no mass and no charge, so gamma is chosen as the one that is not a particle. The question is flawed: ‘delta’ is not a standard emission, and in particle physics the delta (Δ) is itself a particle.

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Correct Answer: (A) Micro waves

Explanation

Microwaves (frequency about 1 to 300 GHz) are used in telecommunication, for example in mobile phone networks, satellite links, radar and Wi-Fi, because they pass through the atmosphere and can be beamed in a line of sight.

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Correct Answer: (A) Acrophobia

Explanation

Acrophobia (from Greek akron, “height”) is an extreme or irrational fear of heights.

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Correct Answer: (D) parabolic concave mirror

Explanation

A car headlight bulb is placed at the focus of a parabolic concave mirror. Rays from the focus become a parallel, powerful beam after reflection. A spherical concave mirror would give a less parallel beam because of spherical aberration.

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Correct Answer: (B) Paleontology

Explanation

Palaeontology is the branch of science that studies fossils, the remains or impressions of ancient organisms preserved in rocks, and so the history of life on Earth.

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Correct Answer: (C) Venus

Explanation

Venus is the standard answer: it rotates clockwise (east to west), opposite to Earth, in a retrograde rotation taking about 243 Earth days, so the Sun rises in the west there. Flag: Uranus is tilted by about 98° and is also described as having retrograde rotation, so the word “only” is open to objection, but Venus is the answer that the question expects.

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Correct Answer: (D) Cryogenics

Explanation

Cryogenics (from Greek kryos, “cold”) is the branch of physics that deals with the production of and the behaviour of materials at very low temperatures (below about −150 °C / 123 K).

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Correct Answer: (A) Vector

Explanation

An organism, usually an insect, that carries a disease-causing agent from one host to another is called a vector. Examples are the female Anopheles mosquito (malaria) and the Aedes mosquito (dengue).

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Correct Answer: (D) Fathometer

Explanation

A fathometer (echo sounder) measures the depth of the sea by sending a sound pulse down and timing its echo from the sea bed. Depth = (speed of sound in water × time)/2.

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Correct Answer: (C) 22

Explanation

The human skull has 22 bones: 8 cranial bones that protect the brain and 14 facial bones. The three tiny bones in each middle ear (ossicles) and the hyoid are counted separately.

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Correct Answer: (B) Jonas Salk

Explanation

Jonas Salk (USA) developed the first successful polio vaccine, an inactivated (killed-virus) injectable vaccine, announced in 1955. Albert Sabin later developed the oral polio vaccine.

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