Question

As blood flows through the capillaries in the lungs, it drops off and picks up .

Answer 1

Answer: The correct answer is-

As blood flows through the capillaries in the lungs, it drops off and picks up carbon dioxide and oxygen respectively.

Deoxygenated blood ( carrying carbon dioxide) reach lungs from right ventricle of heart via pulmonary artery, which decreases diameter and forms capillaries on the alveoli ( tiny air sacs in the lungs for the gaseous exchange).

Thus, oxygen is taken up by the blood ( so as to transport it to the rest  of the body) whereas carbon dioxide ( which is a waste product of metabolism in the body) is dropped at lungs, which is then released out of body through exhalation.

Answer 2

Carbon dioxide is discarded while oxygen is picked up. Thus, blood becomes rich in oxygen again.