JKSSB General Science MCQs

Explanation

• Newton’s First Law of Motion is also called the Law of Inertia.

• It states that a body remains at rest or continues in uniform motion unless acted upon by an external force.

❌ Other options:

• Second Law → Relates force, mass, and acceleration (F = ma)

• Third Law → Action-reaction pairs

• Archimedes’ Principle → Buoyancy in fluids

Explanation

• I. Melting of ice – Physical change ✅

  • Only the state changes (solid → liquid), no new substance is formed.

• II. Cooking food – Chemical change ❌

  • New substances are formed; change is irreversible.

• III. Burning of paper – Chemical change ❌

  • Produces ash, smoke → new substances formed.

• IV. Rusting of iron – Chemical change ❌

  • Iron reacts with oxygen to form iron oxide (rust).

Explanation

Bromine is the only non-metal that exists as a reddish-brown liquid at room temperature. While Mercury (Option A) is also liquid at room temperature, it is a metal, not a non-metal.

Explanation

• Salivary amylase (ptyalin) is present in saliva and begins the digestion of starch in the mouth.

• It converts starch into maltose (simpler sugars).

• This is the first step of carbohydrate digestion in humans.

Explanation

• Amoeba → Belongs to Protista (unicellular eukaryote).

• Hyphae → Thread-like structures forming the body of Fungi.

• Cyanobacteria → Also called blue-green algae, belong to Monera (prokaryotes).

✔️ Hence, all pairs are correctly matched.

Explanation

I. Rose → ❌ Monocotyledon?

• Rose is a dicotyledon, not monocot.

II. Frog → ✅ Amphibian

• Correct. Frogs live both in water and on land.

III. Mango → ❌ Gymnosperm?

• Mango is an angiosperm (dicotyledonous flowering plant), not a gymnosperm.

IV. Shark → ❌ Reptile?

• Shark is a cartilaginous fish (Chondrichthyes), not a reptile.

Explanation

A) In budding, a small protrusion forms on the parent and may stay attached before detaching, while in fragmentation, the parent breaks into pieces, and each piece grows into a new organism. ✅

• Correct. Matches the definitions perfectly.

B) In budding, offspring develop from specialized reproductive cells, whereas in fragmentation, the parent divides under environmental stress to form new organisms. ❌

• Incorrect. Budding does not require specialized reproductive cells, and fragmentation is not necessarily due to stress.

C) In budding, a small part of the parent detaches and grows into an independent organism, whereas in fragmentation, the parent splits into fragments that grow into independent organisms. ✅

• Also correct; similar to A, just worded slightly differently.

D) In budding, the offspring remain attached to the parent for a while, while in fragmentation, the parent breaks into two parts that grow into… ❌

• Incomplete and less precise.

✅ Best answer: A) In budding, a small protrusion forms on the parent and may stay attached before detaching, while in fragmentation, the parent breaks into pieces, and each piece grows into a new organism.

Explanation

A) The microspore and megaspore are diploid (2N) cells that undergo meiosis, and the fertilized zygote remains haploid (N). ❌

• Incorrect. Microspores and megaspores are haploid (N) after meiosis, and zygote becomes diploid (2N).

B) The microspore and megaspore are haploid (N) cells formed after meiosis, and fertilization restores the diploid (2N) number in the zygote. ✅

• Correct. Matches standard plant reproduction.

C) The pollen and ovule mother cells are haploid (N) before meiosis and form diploid gametes after meiosis. ❌

• Incorrect. Mother cells are diploid (2N), not haploid.

D) The pollen and ovule mother cells are diploid (2N), and meiosis produces haploid gametes, but fertilization does not restore the diploid number. ❌

• Incorrect. Fertilization restores the diploid number in the zygote.

Explanation

Step 1: Define the traits and their inheritance

1. Plant height:

   • Tall (T) is dominant, dwarf (t) is recessive.

   Observation: All plants are tall → Offspring genotype cannot be tt

   • So, both parents must have at least one T allele.

2. Seed shape:

   • Round (R) is dominant, wrinkled (r) is recessive.

   Observation: Seed shape ratio = 3 Round : 1 Wrinkled → classic monohybrid cross of heterozygotes

   • So, both parents must be Rr

Step 2: List possible genotypes for plant height

• Tall offspring (all tall) can be produced if:

✅ So possible parental combinations for height: TT × TT, TT × Tt, Tt × TT (unordered = 2 combinations: TT×TT, TT×Tt)

Step 3: Genotypes for seed shape

• Seed ratio 3:1 → monohybrid cross Rr × Rr

Step 4: Combine height and seed shape

• Height × Seed combinations:

We are asked for unordered parental combinations, i.e., consider TT × Tt same as Tt × TT, and Rr × Rr is fixed.

Step 5: Count possible unordered combinations

1. Height combinations (unordered):

• TT × TT

• TT × Tt

2. Seed shape is fixed: Rr × Rr

✅ So, for each height combination, the seed combination is one possibility.

Total possible unordered combinations = 2

Explanation

Mendel’s experiments with Pisum sativum (pea plants):

• He studied 7 traits:

  1. Seed shape

  2. Seed colour

  3. Flower colour

  4. Flower position (axial or terminal)

  5. Pod shape

  6. Pod colour

  7. Stem height

B) Flower shape ❌

• Mendel did not study flower shape; he studied flower colour and position, not shape.

Explanation

A) CFCs destroy ozone and contribute to global warming. ✅

• True. Chlorofluorocarbons (CFCs) catalyze ozone depletion in the stratosphere.

• They are also greenhouse gases, so they contribute to global warming.

B) Ozone depletion directly causes the greenhouse effect. ❌

• Incorrect. Ozone depletion increases UV radiation at Earth's surface, but it does not directly cause the greenhouse effect.

C) Greenhouse gases directly destroy ozone molecules. ❌

• Incorrect. Most greenhouse gases like CO₂, CH₄ do not destroy ozone; ozone depletion is mainly caused by CFCs and halons.

D) Reducing CO₂ emissions alone can fully restore the ozone layer. ❌

• Incorrect. Restoring the ozone layer requires phasing out ozone-depleting substances (CFCs, halons), not just CO₂ reduction.

Explanation

The jumbled food chain: Grasshopper, Grass, Hawk, Frog, Snake

Arrange in proper order:

Grass → Grasshopper → Frog → Snake → Hawk\text{Grass → Grasshopper → Frog → Snake → Hawk}Grass → Grasshopper → Frog → Snake → Hawk

• Grass → Primary producer (autotroph)

• Grasshopper → Primary consumer (herbivore)

• Frog → Secondary consumer

• Snake → Tertiary consumer

• Hawk → Quaternary consumer

Step 2: Energy transfer rule

• Only ~10% of energy is transferred from one trophic level to the next.

• Let the energy content of the frog (secondary consumer) = x kJx \, \text{kJ}xkJ

• Energy available to the primary consumer (grasshopper) = energy two levels below frog

Energy at primary consumer=x×10×10=100x\text{Energy at primary consumer} = x \times 10 \times 10 = 100xEnergy at primary consumer=x×10×10=100x

• Why? Because:

  • Frog energy = 10% of grasshopper energy → Grasshopper energy = 10 × x

  • Grasshopper is one trophic level below frog? Let’s check:

Trophic levels:Grass (P) → Grasshopper (C1) → Frog (C2)\text{Trophic levels:} \text{Grass (P) → Grasshopper (C1) → Frog (C2)} Trophic levels:Grass (P) → Grasshopper (C1) → Frog (C2)

• Frog energy = 10% of grasshopper energy → Grasshopper energy = x/0.1=10xx / 0.1 = 10xx/0.1=10x

✅ Answer: 10x kJ

Explanation

i. Fish showed bioaccumulation of a persistent chemical causing neurological disorders in humans. ✅

• This points to mercury, which bioaccumulates in aquatic food chains and can cause neurological disorders.

• Match: i → a) Mercury

ii. Air contained high levels of a gas that reacts with water to form acid rain. ✅

• The gas that forms acid rain is sulfur dioxide (SO₂).

• Match: ii → b) Sulfur dioxide

iii. Soil had elevated heavy metal concentrations, reducing fertility and causing toxicity in plants. ✅

• Lead is a heavy metal that accumulates in soil and affects plants.

• Match: iii → c) Lead

✅ Correct pairing:

Explanation

A) Plants lack specialized excretory organs, so all metabolic wastes are removed exclusively through stomata by diffusion. ❌

• Incorrect. While plants don’t have organs like kidneys, not all wastes are removed through stomata; some are stored in vacuoles, bark, or leaves.

B) Plants assimilate ammonia into amino acids and can store waste in leaves, bark, and vacuoles. ✅

• Correct. Plants convert toxic ammonia into amino acids or other compounds and can store or sequester wastes in vacuoles, old leaves, or bark.

C) In mammals, the primary nitrogenous waste is uric acid, which requires minimal water for excretion compared to ammonia. ❌

• Incorrect. Mammals primarily excrete urea, not uric acid. Uric acid is excreted mainly by birds and reptiles.

D) Animals and plants both rely mainly on transpiration as their primary mechanism of excretion. ❌

• Incorrect. Transpiration removes some water and volatile wastes, but it is not the main excretion mechanism for animals.

Explanation

A) The ascent of sap in tall trees primarily occurs due to transpiration pull, cohesion, and adhesion forces rather than root pressure alone. ✅

• True. In tall trees, transpiration pull is the main driver of water movement through xylem.

B) Xylem transports water and dissolved minerals mainly in an upward direction, while phloem can transport food both upward and downward. ✅

• True. Xylem is mostly upward; phloem transport is bidirectional depending on source and sink.

C) Phloem transport requires metabolic energy, whereas xylem transport is largely a passive process. ✅

• True. Phloem transport involves active loading/unloading of sugars, while xylem transport is passive.

D) Minerals absorbed by roots move through phloem vessels to reach the leaves where they are utilized for photosynthesis. ❌

• Not correct. Minerals move through xylem, not phloem. Phloem mainly transports organic nutrients like sugars, not minerals.

Explanation

A) Nitrosomonas ❌

• Nitrosomonas is chemoautotrophic; it gets energy by oxidizing ammonia, not parasitic.

B) Amoeba ❌

• Amoeba is heterotrophic, feeding on bacteria and small organisms via phagocytosis, not parasitic.

C) Plasmodium ✅

• Plasmodium is a parasite that lives in human blood and causes malaria. It depends entirely on the host for nutrition.

D) Paramecium ❌

• Paramecium is heterotrophic, feeding on bacteria using cilia, but not parasitic.

Explanation

Step 1: Analyze the metals’ reactivity

• Metal P: Reacts vigorously with water → very reactive metal (like alkali metals)

• Metal Q: Reacts slowly with acids → moderately reactive metal (like zinc, iron)

• Metal R: Does not react with water or acids → least reactive metal (like gold, platinum)

Step 2: Analyze their oxides

• P → PO₂ → metal oxide of a highly reactive metal

• Q → QO → metal oxide of a moderately reactive metal

• R → R₂O → metal oxide of a least reactive metal

Step 3: Decide extraction methods based on reactivity

1. Highly reactive metals (P):

   • Cannot be reduced by carbon (too reactive)

   • Extracted by electrolysis of molten oxide ✅

2. Moderately reactive metals (Q):

   • Can be reduced by carbon (like Fe, Zn, Cu) ✅

3. Least reactive metals (R):

   • Do not react with water or acids

   • Usually found as native metals, no chemical extraction needed ✅

Step 4: Match metals with extraction method

✅ Correct answer: C) P – Electrolysis of molten oxide; Q – Reduction by carbon; R – Native metal, no extraction needed

Explanation

Explanation

A) Commercial Solar panels can only convert 10-12% of sunlight into electricity. ❌

• Incorrect. Modern commercial solar panels have efficiencies between 15% and 22%, and some advanced panels exceed 25%.

B) Wind energy efficiency improves by using larger and more aerodynamically designed blades. ✅

• Correct. Larger blades and improved aerodynamic designs capture more wind energy, increasing efficiency and power output.

C) Tidal energy cannot be harnessed effectively due to the predictability of tides. ❌

• Incorrect. Tidal energy is highly predictable, which is actually an advantage, and it can be harnessed effectively using barrages and turbines.

D) Geothermal energy output is independent of drilling technology and heat extraction methods. ❌

• Incorrect. Geothermal energy output heavily depends on drilling technology, reservoir access, and heat extraction methods.

Explanation

A) Thermal power plants cannot exceed 35% efficiency, even with advanced boiler technology. ❌

• Incorrect. With supercritical and ultra-supercritical boilers, coal-fired power plants can achieve efficiencies up to 45% or more.

B) Supercritical and ultra-supercritical boilers allow coal power plants to achieve higher efficiency. ✅

• Correct. These boilers operate at higher pressure and temperature, improving thermal efficiency and reducing fuel consumption.

C) Hydroelectric power plants cannot improve energy output once the dam is built. ❌

• Not entirely true. Output can be improved by turbine upgrades, better control systems, or optimizing water management, even after construction.

D) Efficiency of petroleum refining is solely determined by the quality of crude oil, not technology. ❌

• Incorrect. Refinery efficiency depends on both crude quality and the refining technology used.

Explanation

Generally, when a metal reacts with an acid, hydrogen is released. However, nitric acid is so strong that it usually oxidizes the hydrogen ($H_2$) into water ($H_2O$) and reduces itself into various nitrogen oxides (like $NO$, $NO_2$, or $N_2O$).

The only two exceptions are Magnesium (Mg) and Manganese (Mn), which react with very dilute nitric acid to produce hydrogen gas:

$$Mg(s) + 2HNO_3(aq) \rightarrow Mg(NO_3)_2(aq) + H_2(g)$$

Explanation

A) Plasma membrane is selectively permeable that regulates the movement of nutrients into and out of the cell. ✅

• True. The plasma membrane controls what enters and exits the cell.

B) Cell interior contains many specialized membrane-bound organelles. ✅

• True. Eukaryotic cells have organelles like nucleus, mitochondria, ER, etc.

C) Mitochondria are organelles responsible for energy transactions needed for cell survival. ✅

• True. Mitochondria produce ATP, the energy currency of the cell.

D) Ribosomes are membrane-bound organelles responsible for protein synthesis. ❌

• Not true. Ribosomes are not membrane-bound; they are either free in cytoplasm or attached to the rough ER. They are responsible for protein synthesis, but they are non-membranous organelles.

Explanation

1. Find the Focal Length ($f$)

The power of the lens ($P$) is given as $+5$ D. The focal length is the reciprocal of the power:

$$f = \frac{1}{P} = \frac{1}{+5} = 0.2 \text{ m} = 20 \text{ cm}$$

Since the power is positive, it confirms the lens is a convex (converging) lens.

2. Use the Lens Formula

Given:

• Object distance ($u$) = $-50 \text{ cm}$ (By sign convention, $u$ is always negative)

• Focal length ($f$) = $+20 \text{ cm}$

The lens formula is:

$$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$$

Substituting the values:

$$\frac{1}{v} - \frac{1}{-50} = \frac{1}{20} \implies \frac{1}{v} + \frac{1}{50} = \frac{1}{20}$$

$$\frac{1}{v} = \frac{1}{20} - \frac{1}{50}$$

Find a common denominator (100):

$$\frac{1}{v} = \frac{5 - 2}{100} = \frac{3}{100}$$

$$v = \frac{100}{3} \approx 33.33 \text{ cm}$$

3. Calculate Magnification ($m$) and Image Height ($h_i$)

The magnification formula for a lens is:

$$m = \frac{v}{u} = \frac{h_i}{h_o}$$

Given the object height ($h_o$) is $2 \text{ m}$:

$$m = \frac{100/3}{-50} = \frac{100}{3 \times -50} = -\frac{2}{3} \approx -0.667$$

Now, find the image height ($h_i$):

$$h_i = m \times h_o = -\frac{2}{3} \times 2 \text{ m} = -\frac{4}{3} \text{ m} \approx -1.33 \text{ m}$$

4. Determine Nature of the Image

• Real and Inverted: Since the magnification ($m$) is negative, the image is real and inverted.

• Diminished: Since $|m| < 1$, the image is smaller than the object ($1.33 \text{ m}$ vs $2 \text{ m}$).

• Position: The positive value of $v$ indicates the image is formed on the other side of the lens.

Explanation

1. Metal rod heated at one end:

• Heat travels through the rod material itself, from the hot end to the cold end.

• This is conduction, because it occurs via direct transfer of kinetic energy between particles in the solid.

2. Sealed glass flask over a flame:

• Water inside the flask circulates as it heats up, forming currents.

• Heat is transferred through the water via movement of the fluid → convection.

• Radiation from the flame also contributes, but the main mode inside the water is convection.

Explanation

✅ Correct Answer: D) Indus

The Chenab River is one of the major tributaries of the Indus River.

It originates from the confluence of the Chandra River and Bhaga River in Himachal Pradesh, flows through Jammu and Kashmir, and then enters Pakistan where it ultimately joins the Indus system.

✔ Therefore, the Chenab River belongs to the Indus river system.

Explanation

✅ Correct Answer: D) BCG vaccine

Under India’s Universal Immunization Programme, the BCG vaccine is given at birth (or as early as possible after birth) to protect infants from severe forms of Tuberculosis, especially tuberculous meningitis and miliary TB.

Why the other options are incorrect:

• Oral Polio Vaccine – First dose may be given at birth, but it protects against polio, not tuberculosis.

• Rotavirus vaccine – Given later (around 6 weeks).

• Human papillomavirus vaccine – Given to adolescents to prevent cervical cancer.

✔ Therefore, the vaccine strictly for tuberculosis at birth is BCG.

Explanation

✅ Correct Answer: C) Bathrooms, kitchens, and laundry activities, excluding toilets

Greywater refers to relatively less contaminated household wastewater generated from activities such as bathing, washing clothes, and kitchen use, but not from toilets.

Sources typically include:

• Showers and bathtubs

• Bathroom sinks

• Washing machines

• Kitchen sinks

Toilet wastewater is called Blackwater, which contains higher levels of pathogens.

Greywater can often be treated and reused for purposes like gardening or flushing toilets, helping conserve water in sanitation systems.

Explanation

Evaluate each statement:

I. Both acidic and basic solutions conduct electricity because they produce ions in aqueous solutions.
✔ Correct – Acids and bases ionize in water, allowing electric current to pass (electrolytes).

II. Antacids are weak bases that neutralize excess stomach acid.
✔ Correct – Many antacids contain bases like Magnesium hydroxide or Aluminium hydroxide.

III. Acidic solutions turn red litmus paper blue.
❌ Incorrect – Acids turn blue litmus red, not red litmus blue.

IV. Phenolphthalein remains colourless in acidic solution but turns pink in basic solution.
✔ Correct.

V. Tooth decay starts when the pH of the mouth is above 8.5.
❌ Incorrect – Tooth decay begins when the pH falls below about 5.5, not above 8.5.

✅ Incorrect Statements: III and V.

Explanation

Match each gland with its correct function:

1. Hypothalamus → Controls the pituitary gland → d

2. Thymus → Large in infants, shrinks with age; trains T-cells → c

3. Thyroid gland → Regulates metabolism → a

4. Pineal gland → Regulates sleep patterns (melatonin secretion) → b

✅ Correct Match:
i – d, ii – c, iii – a, iv – b

Explanation

Evaluate each statement about the Convex Mirror used as a rear-view mirror:

I. It always forms an erect and diminished image.
✔ Correct – A convex mirror always produces a virtual, erect, and smaller (diminished) image of objects.

II. It has a wider field of view as it is curved outwards.
✔ Correct – Because it bulges outward, it allows the driver to see a larger area behind the vehicle, which improves safety.

III. It forms a real image of the objects behind.
❌ Incorrect – A convex mirror forms virtual images, not real ones.

✅ Correct Option: I and II only.