General Science MCQ Practice

• Why correct: Polio and chickenpox are caused by viruses, which are non-cellular infectious agents that hijack host cells to replicate.
• Key concept: Viruses require living hosts; they are not bacteria, protozoa, or algae.
• Brief logic: If a disease is caused by a virus, antibiotics do not work; antiviral strategies target viral replication.

Exam tip: Remember V for Virus—polio and chickenpox are classic viral diseases.

Why others are incorrect: Bacteria, protozoa, and algae are cellular organisms usually treated with antibiotics or antifungals, and they are not the causative agents for polio or chickenpox.

• Why: A hygrometer measures atmospheric moisture or humidity.
• Key concept: Relative Humidity (RH) ≈ (actual vapor pressure / saturation vapor pressure) × 100.
• Other options: Barometer = air pressure; Anemometer = wind speed; Thermometer = temperature.

• Correct option: B — increases.
• When iron rusts, it combines with oxygen from air to form iron oxide. This adds oxygen mass to the sample, so the total weight increases.
• Key concept: oxidation and mass gain from oxygen uptake (Fe + O2 → Fe2O3; oxygen atoms are added).
• Formula note: the rust mass ≈ original Fe mass + mass of absorbed O2.
• Exam tip: remember rusting is a chemical reaction with oxygen; weight change is due to oxygen incorporation, not loss of iron.
• Other options are incorrect because rusting does not remove iron mass nor first increase then decrease.

• Explanation: Tuberculosis is commonly called "white plague" due to the pale, wasted appearance of patients and the historical term from 19th‑century medicine.
• Key concept: TB is a chronic infectious disease caused by Mycobacterium tuberculosis, affecting lungs primarily.
• Why others are incorrect: Typhoid is a severe enteric fever; malaria is a mosquito‑borne fever with fever cycles; plague refers to Yersinia pestis infections.
• Exam tip: Remember “white” links to pallor in TB; infectious diseases often labeled by symptoms/appearance.

• Allotropes of carbon are different structural forms of carbon (same element) like diamond, graphite, and C60 (buckminsterfullerene).
• Methane (CH4) is a compound, not an allotrope of carbon, since it contains hydrogen.
• Correct answer: D — Methane is not an allotrope. Diamond (sp3), Graphite (sp2), and C60 are pure carbon allotropes.

• Why: Vitamin-B and Vitamin-C are water-soluble; they dissolve in water and are not stored in large amounts—excess is excreted in urine.
• Key concept: Water-soluble vitamins (B-complex and C) require regular intake; fat-soluble vitamins (A, D, E, K) are stored in body fat/liver.
• Why others are incorrect: A includes fat-soluble A; C includes D; D includes A & K—both are fat-soluble.
• Exam tip: Remember “B and C” are water-soluble; “A, D, E, K” are fat-soluble.

• Correct option: A. Liver
• Why: Hepatitis is inflammation of the liver. The liver performs detoxification, bile production, and metabolism.
• Key concept: Organ-specific disease: inflammation targets the liver muscles/organs listed.
• Exam tip: If a disease mentions “hepat-” or liver function, choose liver first.
• Why others are incorrect: Pancreas, spleen, and small intestine are not the primary targets of hepatitis.

• The Earth's crust contains aluminium as the most abundant metal by weight (about 8%), though oxygen and silicon are most abundant overall elements.
• Key concept: crustal abundance is about element composition; metals vary in abundance after non-metals.
• Other options are less abundant metals in the crust: zinc, copper, and iron occur in smaller amounts than aluminium.
• Exam tip: remember “Al” is the most common metal in the crust; iron is abundant but not the top metal.

• Reason: Exosphere is the outermost layer of Earth's atmosphere, gradually blending into space at high altitudes (roughly 700–10,000 km).
• Key concept: Atmospheric layering includes troposphere, stratosphere, mesosphere, thermosphere, and exosphere; the exosphere marks the boundary with space.
• Tip: No sharp end to layers; transitions are gradual.
• Why others are incorrect: Stratosphere is below, Mesosphere is middle, Ionosphere is a region within the upper atmosphere/thermosphere with ionized particles, not the outermost layer.

• Key concept: Itai-Itai disease is caused by chronic cadmium poisoning, leading to severe kidney damage and softening of bones.
• Why correct: Cadmium accumulates in the body from contaminated water/food and affects kidneys and bones, producing the characteristic pain and weakness.
• Other options:
  • Nickel, chromium, mercury do not cause Itai-Itai disease.
• Tip: Remember cadmium toxicity is linked to renal + skeletal damage.