✓ (ii) WAV — WAV (Waveform Audio File Format) is an audio file format. MOV and 3GP are video formats, and SVI is a Samsung video format. Other audio formats include MP3, AAC, FLAC, OGG.

✓ (iv) Thymine — The figure shows DNA. Thymine (T) is found only in DNA; in RNA it is replaced by Uracil (U). Adenine, Guanine, and Cytosine are found in both DNA and RNA.

✓ (iv) Have beak and feathers — The defining characteristic of Aves (birds) is having a beak (bill) and feathers on the body. Birds breathe through lungs, are warm-blooded (homeothermic), and lay eggs (oviparous).

✓ (iii) 35 N — Upthrust (Buoyant Force) = Weight in air − Weight in liquid = 50 N − 15 N = 35 N. This is Archimedes' Principle: the upthrust equals the weight of the fluid displaced.

✓ (ii) 1.24 × 10⁸ m/s — The refractive index of diamond is about 2.42. Speed of light in diamond = c/n = 3 × 10⁸ / 2.42 ≈ 1.24 × 10⁸ m/s. Diamond slows light significantly, causing its brilliant sparkle.

✓ (ii) 4 s — Time to reach maximum height: t = u/g = 20/10 = 2 s. Total time in air (up + down) = 2 × 2 = 4 seconds. (Using g = 10 m/s²)

✓ (i) Kerosene has higher temperature than water — Water has a much higher specific heat capacity (4200 J/kg°C) than kerosene (~2000 J/kg°C). Given the same heat and same mass, kerosene rises to a higher temperature (Q = mcΔT, so ΔT = Q/mc — smaller c means larger ΔT).

✓ (iv) Motor effect — When a current-carrying conductor is placed in a magnetic field, it experiences a force (Fleming's Left Hand Rule). This is the motor effect, the principle behind electric motors. The conductor moves/vibrates due to the interaction of the current and magnetic field.

✓ (i) Chalcopyrite (CuFeS₂) — Chalcopyrite is the most important ore of copper. Argentite (Ag₂S) is silver ore, Hematite (Fe₂O₃) is iron ore, and Bauxite (Al₂O₃) is aluminium ore.

✓ (i) Statement and Argument 2 are correct but Argument 1 is incorrect — Persistent (bio-accumulative) insecticides collect in the environment because they degrade gradually (slowly) in contact with air and water (Argument 2 ✓). Argument 1 says they don't degrade quickly — but the real mechanism is gradual degradation, not zero degradation, so Argument 1 is incorrect as phrased. The statement is correct: they are a type of insecticide that accumulates.

(a) Force = mass × acceleration → Unit: Newton (kg·m/s²). Fundamental units: kilogram (kg), metre (m), second (s).

(b) Both Aves and Mammals are warm-blooded (homeothermic) — they maintain constant body temperature. Both also have a 4-chambered heart.

(c) The hybrid animal produced by crossing a zebra and a horse is called a Zorse (Zebroid).

(d) Establish national parks, wildlife reserves, and conservation areas to provide protected habitats for endangered animals (e.g., Chitwan National Park for one-horned rhinos).

(e) Hydraulic lift / Hydraulic press / Hydraulic brake — all work on Pascal's law (pressure applied at one point is transmitted equally throughout the fluid).

(f) Anomalous expansion of water: water expands on cooling from 4°C to 0°C, so ice floats on water. This insulates the bottom of lakes/ponds, allowing aquatic life to survive in winter.

(g) 2Mg + O₂ → 2MgO
Magnesium burns in oxygen to form magnesium oxide (white powder).

(h) Roasting: Heating sulphide ore in excess air/oxygen, converting it to metal oxide (used for sulphide ores). Calcination: Heating carbonate or hydroxide ore in limited/no air to get metal oxide (used for carbonate ores).

(i) The structural formula shows CH₃–CH₂–OH (ethane + OH group). IUPAC name: Ethanol (Ethan-1-ol).

Independent Variable: The amount of stretch of the rubber band (how much the rubber is stretched). This is what we control/change.

Dependent Variable: The distance traveled by the paper piece (how far the paper flies). This changes depending on the stretch of the rubber band.

Note: Controlled variables would include the mass of the paper, the type of rubber band, direction of throw, etc.

Basis	Rat (मुसो)	Snake (सर्प)
Heart Structure	4-chambered heart (2 auricles + 2 ventricles) — complete separation of oxygenated and deoxygenated blood	3-chambered heart (2 auricles + 1 ventricle) — mixing of oxygenated and deoxygenated blood
Reproduction	Viviparous — gives birth to live young (directly bears young)	Oviparous — lays eggs (some are ovo-viviparous)

1. Pollination: Honey bees are the most important pollinators. When they collect nectar from flowers, pollen sticks to their bodies and transfers to other flowers, enabling cross-pollination, which is essential for fruit and seed production in crops and wild plants.

2. Honey and Wax Production: Honey bees produce honey (a nutritious food used medicinally and commercially) and beeswax (used in cosmetics, candles, and medicines), making beekeeping (apiculture) an important cottage industry.

Cross: Tt × TT (Hybrid Tall × Pure Tall)

Result: All offspring (100%) are tall.

• 50% TT (Pure Tall) — Homozygous dominant
• 50% Tt (Hybrid Tall) — Heterozygous
• Phenotype ratio: 4 Tall : 0 Dwarf (All Tall)
• Genotype ratio: 2 TT : 2 Tt

Non-granular (Agranulocytes) leucocytes do not have visible granules in their cytoplasm. Two examples:

1. Lymphocytes — Produce antibodies and are involved in immune response (B-cells and T-cells).

2. Monocytes — The largest WBCs; they engulf pathogens and dead cells by phagocytosis; differentiate into macrophages.

1. Cultivation and Propagation: Encourage local farmers and communities to cultivate medicinal plants (like Neem, Turmeric, Ginger, Yarshagumba) in kitchen gardens and community farms to ensure sustainable supply and reduce pressure on wild populations.

2. Awareness and Training: Organize training programs about the identification, proper harvesting, processing, and therapeutic uses of local medicinal plants so communities can use them effectively for primary healthcare and generate income.

Given: Mass lifted on Earth = 100 kg, g on Earth = 10 m/s², g on Moon = 10/6 ≈ 1.67 m/s²

Maximum Force (effort) the person can exert:

F = m_Earth × g_Earth = 100 × 10 = 1000 N

Mass lifted on Moon with same force (1000 N):

m_Moon = F / g_Moon = 1000 / (10/6) = 1000 × 6/10 = 600 kg

∴ The person can lift 600 kg on the Moon (6 times more than on Earth).

1. Keeps objects on Earth's surface: Gravity pulls all objects toward the center of the Earth, giving them weight and keeping them on the ground. Without gravity, everything would float away.

2. Maintains planetary orbits and tides: Gravitational force keeps planets in orbit around the Sun and the Moon in orbit around the Earth. It also causes ocean tides (Moon's gravity pulls Earth's oceans).

Given: m = 8 kg, T₁ = 30°C, T₂ = 48°C, c = 4200 J/kg°C

ΔT = T₂ − T₁ = 48 − 30 = 18°C

Formula: Q = mcΔT

Q = 8 × 4200 × 18

Q = 8 × 75600

Q = 604,800 J = 6.048 × 10⁵ J

∴ Heat required = 604,800 Joules (604.8 kJ)

1. Light must travel from a denser medium to a rarer medium (e.g., from glass to air, or from water to air).

2. The angle of incidence must be greater than or equal to the critical angle for that pair of media. When the angle exceeds the critical angle, all light is reflected back into the denser medium — total internal reflection occurs.

Applications: Optical fibers, diamonds sparkle, mirages, periscopes.

Basis	Closed Universe (बन्द ब्रह्माण्ड)	Open Universe (खुला ब्रह्माण्ड)
Expansion	Expansion of universe eventually stops and reverses — ends in a "Big Crunch"	Universe expands forever without stopping
Density	Average density is greater than the critical density (Ω > 1)	Average density is less than critical density (Ω < 1)

Reaction: Ammonium chloride + Calcium hydroxide → Calcium chloride + Water + Ammonia

Verification (Balancing):
Left: N=2, H=8+2=10→(8+2)=10 ✓, Cl=2 ✓, Ca=1 ✓, O=2 ✓
Right: Ca=1, Cl=2, H=4+6=4+6 → 2H₂O gives 4H, 2NH₃ gives 6H = 10H ✓, N=2 ✓, O=2 ✓ ✓ Balanced!

This reaction is used in the laboratory preparation of ammonia gas by heating the mixture.

Ethane: CH₃–CH₃ → Replace one H from each carbon with –OH

Compound formed: HO–CH₂–CH₂–OH (Ethylene glycol)

IUPAC Name: Ethane-1,2-diol (or 1,2-Ethanediol)

Uses: antifreeze in car radiators, making polyester (PET plastic), coolant.

1. Wear Protective Equipment: Always wear gloves, mask, goggles, and protective clothing while spraying pesticides to prevent skin contact, inhalation, or eye exposure to toxic chemicals.

2. Follow Instructions and Proper Dosage: Use only the recommended amount of pesticide as per the label. Avoid spraying near water sources, on windy days, or before rain to prevent contamination of water bodies and unintended areas.

✅ Two Positive Impacts of Digital Technology:

1. Easy Access to Information and Education: Digital technology gives instant access to the internet, online libraries, educational videos, and e-learning platforms. Students and professionals worldwide can learn and share knowledge easily.

2. Improved Communication and Connectivity: Emails, video calls, social media, and instant messaging connect people globally, enabling fast and affordable communication for personal, business, and emergency purposes.

❌ Two Negative Impacts of Digital Technology:

1. Cybercrime and Privacy Threats: Hacking, phishing, online fraud, and data theft have increased. Personal information, financial data, and national security can be compromised through digital platforms.

2. Social Isolation and Health Problems: Excessive screen time leads to physical problems (eye strain, obesity, poor posture) and mental health issues (anxiety, depression, addiction to social media), reducing face-to-face social interaction.

Identifying Elements:

Element A: 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹ → Total electrons = 2+2+6+2+6+1 = 19 → Potassium (K)

Element B: 1s², 2s², 2p⁶, 3s², 3p⁵ → Total electrons = 2+2+6+2+5 = 17 → Chlorine (Cl)

(i) Metal: Element A (Potassium/K) is the metal. Metals have 1-3 electrons in the outermost shell and tend to lose electrons (K has 1 electron in the 4th shell). Chlorine is a non-metal.

(ii) Period of B (Chlorine): The highest principal quantum number in Cl's configuration is n = 3 (3s², 3p⁵), so Chlorine is in Period 3 of the modern periodic table.

(iii) Balanced Chemical Equation (K + Cl):

Potassium reacts with Chlorine to form Potassium Chloride:

This is an ionic compound: K⁺ Cl⁻ (K loses 1e⁻, Cl gains 1e⁻). This is a combination/synthesis reaction.

Gas produced: Egg shells are made of CaCO₃. Reacting with HCl (dilute acid) produces CO₂ gas.
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑

(i) CO₂ passed into lime water [Ca(OH)₂]:

Lime water turns milky/white (CaCO₃ precipitates). Excess CO₂ makes it clear again: CaCO₃ + H₂O + CO₂ → Ca(HCO₃)₂ (soluble)

(ii) Medical Application of CO₂: CO₂ is used in fire extinguishers and in medicine as a component in carbogen (95% O₂ + 5% CO₂) to stimulate breathing in respiratory patients. It is also used in laparoscopic surgery (to inflate the abdominal cavity for better visibility).

(iii) Gas with molecular mass 17 a.m.u. = NH₃ (Ammonia) (N=14, H=1×3=3 → 17 a.m.u.)

CO₂ + NH₃ reaction:

Molecular formula of compound (Urea): CO(NH₂)₂ or CH₄N₂O

(iv) Test for CO₂: Pass the gas through fresh lime water [Ca(OH)₂ solution]. If the lime water turns milky/white, the gas is CO₂. (Due to formation of insoluble calcium carbonate: CO₂ + Ca(OH)₂ → CaCO₃↓ + H₂O)

Answer: No. 'X' chromosome is NOT absent from the semen. The father's sperms carry either X or Y chromosome in equal proportions (50% X-bearing, 50% Y-bearing). Having four sons is due to chance — each birth had a 50% probability of being a son.

Chart showing Sex Determination in Humans:

Role of Sex Chromosomes: Mother always contributes X chromosome in eggs. Father contributes either X or Y in sperm (50:50). If Y-sperm fertilizes egg → XY = Male (Son). If X-sperm fertilizes egg → XX = Female (Daughter). Thus, the father (male) determines the sex of the child. The four sons were born because by chance, Y-bearing sperms fertilized the eggs in all four pregnancies — X chromosome is still present in 50% of the father's sperms.

Given: Power of lens (P) = −8 D

Focal Length: f = 1/P = 1/(−8) = −0.125 m = −12.5 cm

Type of Lens: Negative power → Concave lens (diverging lens). Concave lenses are used to correct myopia (short-sightedness / nearsightedness).

Two Causes of Myopia (Short-sightedness):

1. Elongated Eyeball: The eyeball is longer than normal from front to back, so light from distant objects focuses in front of the retina instead of on it.

2. Excessive Curvature of the Eye Lens/Cornea: The eye lens or cornea is too curved (too powerful), causing light to converge too early — before reaching the retina. This is also worsened by excessive close-up work (reading, screen use) from an early age.

Bicuspid Valve (Mitral Valve): Located between the Left Atrium and Left Ventricle. Prevents backflow of blood from the left ventricle to the left atrium. Has 2 cusps/flaps.

Pulmonary Valve: Located at the opening of the pulmonary artery from the Right Ventricle. Prevents backflow of blood from the pulmonary artery back into the right ventricle. Is a semilunar valve.

Given: N_s = 10 × N_p, V_p = 230 V

Formula: V_s/V_p = N_s/N_p

V_s = V_p × (N_s/N_p) = 230 × 10 = 2300 V

Type: Since V_s > V_p and N_s > N_p, this is a Step-Up Transformer.

Use of Step-Up Transformer: Used in power transmission lines — electricity generated at power stations (e.g., 11 kV) is stepped up to high voltage (e.g., 132 kV or 400 kV) to reduce energy loss during long-distance transmission. Also used in X-ray machines, electric arc furnaces, and high-voltage experiments.