Natural Science CLEP Prep 2025 – 400 Free Practice Questions to Pass the Exam

The heart's main function is to circulate oxygen-rich blood throughout the body. This is necessary for the delivery of oxygen and nutrients to all cells, tissues, and organs in order to maintain their proper function. Option B is partially correct as the heart also pumps nutrients, but this is not its primary function. Option C is incorrect as the brain receives oxygen-rich blood from the heart, not the other way around. Finally, option D is incorrect as the heart does not circulate ocean water, it only circulates blood.