PPSC Past Papers & Solved MCQs

The correct answer is Dental enamel because it is the most highly mineralized and toughest tissue found anywhere in the human anatomy.

• Step 1 (Mineral Composition): Dental enamel forms the visible outer shell coating of each tooth. It consists of roughly 96% inorganic mineral content, primarily composed of tightly packed crystalline calcium phosphate known as hydroxyapatite.
• Step 2 (Structural Strength): This extreme mineral density makes enamel harder than steel or any skeletal bone tissue, providing an essential shield that protects inner tooth layers from daily biting forces and thermal stress.
• Incorrect Options:
  • Skull bones is incorrect because while skull plates are reinforced to protect the brain, bone tissue contains significantly more organic collagen matrices, making it softer than enamel.
  • Ribs is incorrect because ribs are semi-flexible bones designed with a porous interior to shield vital organs while bending slightly to allow breathing.
  • None of these is incorrect because dental enamel is the true, scientifically proven answer.

The correct answer is High because colder temperatures increase air density, causing gas molecules to pack closely together and sink toward the Earth's surface.

• Step 1 (Molecular Density): When air cools down, the gas molecules lose kinetic energy, move slower, and contract. This tight packing increases the overall density and weight of the air mass.
• Step 2 (Pressure Generation): Because dense, cold air is heavy, it naturally sinks toward the ground. This downward gravitational force exerts greater weight against the Earth's surface, creating a high-pressure zone.
• Incorrect Options:
  • Low is incorrect because low atmospheric pressure zones are created by warm temperatures, which expand air molecules and cause them to rise rapidly.
  • Normal is incorrect because pressure is always in a state of dynamic change based directly on thermal variations, rather than remaining static.
  • None of these is incorrect because option 2 is the exact scientific rule of thermodynamics.

The correct answer is Capillary action because the narrow microscopic spaces embedded within the paper fibers pull liquids upward against the force of gravity.

• Step 1 (Microscopic Matrix): Blotting paper is intentionally manufactured with a highly porous structure using loosely woven cellulose wood fibers. These interlaced pathways act like thousands of tiny, interconnected capillary tubes.
• Step 2 (Fluid Mechanics): When a liquid contacts the paper, the adhesive forces between the liquid molecules and the cellulose walls are stronger than the cohesive forces inside the fluid itself. This imbalance naturally draws the fluid rapidly up into the empty spaces.
• Incorrect Options:
  • Viscosity is incorrect because viscosity measures a fluid's internal resistance to flow or thickness, which works to slow down absorption rather than aiding it.
  • Surface tension is incorrect because surface tension is the cohesive force that holds a liquid's surface layer together, minimizing surface area, though it interacts with capillary pull.
  • None of these is incorrect because capillary action is the exact physical mechanism responsible.

The correct answer is Emphysema because chronic exposure to tobacco smoke permanently destroys the delicate walls of the air sacs (alveoli) inside the lungs.

• Step 1 (Alveolar Damage): Tobacco smoke contains toxic chemicals that trigger severe chronic inflammation inside the lungs. This destructive process breaks down the elastic fibers safeguarding the walls of the alveoli.
• Step 2 (Impact on Respiration): As these internal walls rupture, tiny air pockets merge into larger, inefficient spaces. This drastically shrinks the available surface area for oxygen exchange, trapping stale air in the lungs and causing progressive shortness of breath.
• Incorrect Options:
  • Tuberculosis is incorrect because it is a contagious infectious disease caused directly by a specific bacterium (Mycobacterium tuberculosis), not by smoking habits.
  • Asthma is incorrect because asthma is primarily a chronic inflammatory airway disease characterized by bronchial hyper-responsiveness triggered by allergens, genetics, or environmental irritants.
  • None of these is incorrect because emphysema is a major component of smoking-induced Chronic Obstructive Pulmonary Disease (COPD).