General Science MCQ Practice

• Why correct: King cobras are known to construct and guard a nest for their eggs, a rare nesting behavior among snakes.
• Key concept: parental care in reptiles; nest-building for egg incubation and protection.
• Other options: Krait, Chain viper, and Saw-scaled viper lay eggs but do not build nests or show active nesting behavior.
• Tip: Remember “nest-building = king cobra” for fast recall in exams.

• Reason: Cow milk is a rich source of water-soluble B vitamins, especially riboflavin (B2) and cobalamin (B12), making Option B correct as a general “Vitamin B” source.
• Key concept: Vitamins B1, B2, B12 are common in dairy; they support energy metabolism and red blood cell formation.
• Tip: If a question asks for “Vitamin B” in dairy, milk is a strong choice; specify B2 or B12 for precision.
• Why others are incorrect: Vitamin A (retinol) and D are present in smaller amounts; Vitamin C is negligible in milk.

• Acupuncture involves inserting needles into specific body points to relieve pain.
• Key concept: stimulation of acupuncture points to modulate pain signals.
• Why others are incorrect: A describes herbal medicine; C is surgical, not acupuncture; D is false.
• Exam tip: Remember “needles at points” as the defining feature of acupuncture for pain relief.

• The SA node generates rhythmic electrical impulses that set the heart rate, acting as the natural “pacemaker.”
• Key concept: automaticity and rhythmic rhythm generation in the sinoatrial node.
• Why others are wrong: Autoregulator, Time controller, and Beat regulator are not standard terms for initiating heartbeats.
• Exam tip: Remember “SA node = pace-maker” as the primary initiator of heartbeat. No formula needed.

• Why: Vulcanization uses sulfur to form cross-links (C–S–C) between polymer chains, improving elasticity and heat resistance of rubber.
• Key concept: Cross-linking in polymers; sulfur forms polysulfide bridges with polyisoprene chains.
• Formula/numerical note: S8 rings break and create S–C bonds to link chains; no numerical calculation needed here.

• Why correct: Lenses are often made of flint glass because it has a high refractive index and significant dispersion, which helps in correcting chromatic aberration when combined with crown glass in achromatic lenses.
• Key concept: Optical dispersion and refractive index (n) control how different colors bend. Abbe number (V) indicates dispersion; flint glass has lower V (more dispersion) than crown glass.
• Tip: For sharp, color-free images, achromatic doublets use crown + flint glass to cancel dispersion.
• Why others are incorrect: Pyrex is mainly for heat resistance; ordinary glass has lower dispersion; cobalt glass is colored and not used for precision lenses.

• The blue colour of the sky is due to scattering of sunlight by atmospheric molecules.
• In Rayleigh scattering, shorter wavelengths (blue) scatter more than longer wavelengths (red). The scattered blue light comes from every direction, making the sky look blue.
• Key concept: scattering cross-section ∝ 1/λ^4 (short wavelengths scatter strongly).
• Why others are wrong:
  • Interference – not the cause of the sky colour in daylight.
  • Reflection – sky colour is not from surface reflection.
  • Refraction – changes direction, not dominant colour source.

• Why: A mirage forms when light passes through air layers with changing refractive index, bending (refraction) as it travels. In hot surfaces, rays may bend so much they undergo total internal reflection at layer interfaces, creating an apparent image below or displaced from the real object.
• Key concept: Snell’s law (n1 sin θ1 = n2 sin θ2) governs refraction; critical angle for TIR determines when rays reflect internally.
• Formula: sin θc = n2/n1 (for TIR).

• Correct: second incisor. Elephant tusks are elongated, permanently growing incisor teeth, not canines, premolars, or molars.
• Key concept: tusks are modified incisors (upper jaw). In elephants, incisors become tusks and keep growing throughout life.
• Why others are wrong:
  • A. canines — tusks are not canines.
  • B. premolar & D. molar — these are cheek teeth, not tusks.

Exam tip: Remember “tusk = incisor” for elephant anatomy.

• Whale (specifically the blue whale) is the largest mammal ever known, living or extinct, with lengths up to ~30 m and weights over 150 tons.
• Key concept: among mammals, body size varies; whales are among the largest due to aquatic lifestyle and abundant food.
• Why others are incorrect: elephants are very large but smaller than whales; rhinoceroses are much smaller; dinosaurs are not mammals.
• Exam tip: remember “largest mammal = blue whale” for contrast with “largest land animal” being elephants for other questions.