Assertion (A): Alveoli contain an extensive network of blood vessels.
Reason (R): Alveoli is the site where exchange of gases occurs.

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is NOT the correct explanation of A.
C. A is true but R is false.
D. A is false and R is true.

Answer

A

Explanation

The alveoli of lungs are richly supplied with blood and are the sites where exchange of gases (`O_(2)` and `CO_(2)`) occurs between blood and atmosphere.