what function do capillaries serve in the cardiovascular system?\na. carry blood to the brain\nb. return…

Brief Explanations:

Capillaries are the smallest blood vessels. They have thin walls which allow for the exchange of substances like oxygen, carbon dioxide, and heat. When the body is hot, blood flow through capillaries near the skin's surface increases, allowing heat to be dissipated (helping control body temperature).

• Option A: Arteries (like the carotid artery) carry blood to the brain, not capillaries.
• Option B: Veins (like the pulmonary veins in a different context) return blood to the heart (and then to the lungs in pulmonary circulation, but not in the way described here). Capillaries are for exchange, not just return.
• Option D: Old blood cells are mainly replaced in the bone marrow (for red blood cells) and spleen (for some breakdown and recycling processes), not by capillaries.

Answer:

C. help control body temperature