Collateral circulation in the heart allows bypass of the pulmonary circulation before birth. a. helps return blood from the lungs to the left atrium. b. may allow bypass of a blocked coronary artery. c. branches directly from the ascending aorta. d. directly returns blood to the inferior vena cava.

Option B, may allow bypass of a blocked coronary artery.

Explanation:

Collateral circulation consists of a network of tiny blood vessels which are nit functional under normal conditions. However, they become functional in case of coronary artery disease.  

In coronary artery disease, the coronary arteries narrow down leading to blockage and stopping the flow of blood in the muscles of heart.  

In this condition, the collateral circulatory network allows flow of blood around and within the blocked artery thereby protecting heart tissue from injury

Hence, option B is correct

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