Given below are two statements: one is labelled Assertion (A) and other is labelled Reason (R).
Assertion (A): Normal expiration is a passive process in humans.
Reason (R): Expiration in humans involves the contraction of external intercostal muscles.
In light of the above statements, choose the correct answer from the options given below.

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(A) is correct but (R) is not correct.

Both (A) and (R) are correct but (R) is not the correct explanation of (A).

Both (A) and (R) are correct and (R) is the correct explanation of (A).

Both (A) and (R) are incorrect.

answer is C.

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Detailed Solution

Assertion (A) is true: Expiration (exhalation) in humans is generally considered a passive process, meaning it doesn't require significant muscular effort under normal circumstances. The muscles of the ribcage and diaphragm relax, causing the lung volume to decrease, which leads to the expulsion of air.
Reason (R) is also true: Inspiration (inhalation) involves the contraction of the external intercostal muscles. When these muscles contract, they lift the ribcage upward and outward, expanding the chest cavity and creating a negative pressure that draws air into the lungs.
The reason (R) doesn't explain why expiration is a passive process. Expiration being passive is primarily due to the relaxation of muscles involved in inhalation (like the diaphragm and external intercostal muscles), allowing the lungs to recoil and expel air without active muscular contraction.
(A) is true, but (R) is false.

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