Human Respiratory System MCQs

Q1. Why is the surface of the lungs folded into millions of alveoli?

• A.to store more air permanently
• B.to maximise the area for gas exchange
• C.to make the lungs heavier
• D.to filter the blood

Answer: B. to maximise the area for gas exchange

Q2. Consider the following statements about the respiratory system: (I) Gas exchange occurs in the alveoli. (II) Haemoglobin carries oxygen. (III) The trachea has no cartilage support. Which of the above statement(s) is/are correct?

• A.None of these
• B.Only III
• C.Only I
• D.Only I and II

Answer: D. Only I and II

NCERT fact (biology, chapter 'Life Processes'): Correct: I, II. Why option D fits - Correct. Distractor analysis: option A) 'None of these' misses the point - Re-check each statement individually; option B) 'Only III' misses the point - Re-check each statement individually. Final answer - D) Only I and II.

Q3. Cellular respiration uses the oxygen delivered by breathing to:

• A.make glucose
• B.digest proteins
• C.release energy from glucose
• D.produce chlorophyll

Answer: C. release energy from glucose

To see why, recall that An ionic bond forms when a metal donates electrons to a non-metal: e.g. Na -> Na+ + e-, Cl + e- -> Cl-, and Na+ + Cl- -> NaCl; the resulting solid is held by strong electrostatic attraction => this fixes the property asked in the stem; hence the answer = release energy from glucose. That fits the listed correct option directly - Correct. As for the rest: option A) 'make glucose' fails since Glucose is broken down, not made, in respiration; option B) 'digest proteins' doesn't hold - It releases energy from glucose. Hence the answer is C) release energy from glucose.