Which of the following statements are correct in reference to the role of A (shown in the given diagram) during a breathing cycle in human beings?

(i) It helps to decrease the residual volume of air in lungs.
(ii) If flattens as we inhale.
(iii) It gets raised as we inhale.
(iv) It helps the chest cavity to become larger.
(a) (ii) and (iv)
(b) (iii) and (iv)
(c) (i) and (ii)
(d) (i), (ii) and (iv)

(a) (ii) and (iv)

Explanation:

During inhalation, we lift our ribs and flatten our diaphragm (A), which enlarges the chest cavity. This creates a vacuum that pulls air into the lungs, filling the expanded alveoli. When we exhale, our ribs and diaphragm return to their normal positions, causing the chest cavity to shrink. This pushes air out of the lungs.

• The lungs always retain a residual volume of air, ensuring there is enough time for oxygen absorption and carbon dioxide release.
• This residual volume remains constant under normal conditions.