RRB Group D — 28 Nov 2025 — Shift II — Official Paper — Kerala PSC PYQ Practice with Answers

Correct answer (Option A): Hormonal contraceptive pills contain synthetic versions of female sex hormones (estrogen and progesterone). By introducing these external hormones, they override the body's natural endocrine feedback loops to inhibit ovulation and alter cervical mucus. Because hormones act globally as chemical messengers, this disruption can influence other physiological systems, leading to secondary side effects like mood changes, nausea, weight fluctuations, or cardiovascular symptoms. Option A is correct. Why others are wrong: Option B is wrong because pills do not destroy existing eggs; they suppress egg release. Option C is incorrect because mechanical blockages are characteristic of barrier methods (like condoms), not oral hormones. Option D is incorrect because the primary pathway is endocrine regulation rather than targeted immune system interference. Study tip: Hormones exert multi-systemic regulatory effects. When analyzing medical or endocrine questions, remember that systemic feedback alteration typically affects multiple organs beyond the primary target.

Correct answer (Option D): Formula: R_total = R₁ + R₂ Formula: I = V / R_total Given values: Resistor 1: R₁ = 15 Ω Resistor 2: R₂ = 5 Ω Voltage: V = 12 V Step-by-step calculation: Step 1: Calculate total equivalent resistance for the series connection. R_total = 15 + 5 = 20 Ω Step 2: Apply Ohm's Law to calculate the circuit current. I = 12 / 20 = 0.6 A Answer: 0.6 A Option D is correct. Why others are wrong: Options A, B, and C provide incorrect current measurements due to math errors or incorrect resistance formulas (such as using parallel rules or mismatched numbers). Study tip: In a series configuration, equivalent resistance is always the simple linear sum of individual resistances, and current remains uniform across all components.

Correct answer (Option C): Thomson's model of the atom, historically termed the 'plum pudding' or water-melon model, proposed that an atom consists of a uniform sphere of positive charge. Negatively charged electrons are embedded randomly within this positive background matrix to maintain overall electrical neutrality. Option C is correct. Why others are wrong: Option A describes elements of Bohr's atomic model. Option B describes the nuclear atomic model established by Rutherford. Option D is historically inaccurate, as neutrons were discovered much later by James Chadwick in 1932. Study tip: Track the chronology of atomic configurations: Thomson (embedded electrons) → Rutherford (nuclear center) → Bohr (quantized electron tracks) → Quantum model.

Correct answer (Option B): To integrate desired multi-trait characteristics like low feed consumption, environmental heat resilience, and enhanced yield metrics, farmers utilize cross-breeding programs. Crossing exotic breeds (known for high growth rate or egg production) with adapted native/local breeds (known for resilience and climate tolerance) produces hybrid varieties exhibiting heterosis or hybrid vigor. Option B is correct. Why others are wrong: Option A outlines basic management without expanding genetic traits. Option C avoids solving poultry goals by pivoting entirely into a different sector. Option D relies exclusively on native lines, which might lack the accelerated growth rates or chick output found in controlled hybrids. Study tip: Hybridization leverages complementary genetic strongsuits across distinct genetic pools to maximize agrarian output and environmental adaptation.

Correct answer (Option C): When light transitions obliquely from air (a rarer optical medium) into glass (a denser optical medium), it refracts toward the normal line, meaning the angle of incidence is greater than the angle of refraction (falsifying statement i). Because glass has a higher refractive index than air, the velocity of the light wavefront drops during transmission (validating statement iii). Upon exit back into air, the lateral shift matches the entry refraction angles, making the entry track and exit track parallel (validating statement iv). Hence, statements (iii) and (iv) are true. Option C is correct. Why others are wrong: Options A, B, and D include incorrect evaluations (statements i or ii), distorting Snell's angular relationships and properties of standard rectangular geometries. Study tip: Light bending behaviors follow structural medium density rules: rarer to denser transitions drop speeds and pinch refractive tracks toward the normal line.