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 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).