What do capillaries primarily facilitate?

The correct answer focuses on the primary function of capillaries, which is facilitating the exchange of gases, nutrients, and waste products between the blood and the surrounding tissues. Capillaries are tiny blood vessels that form a network throughout the body, allowing for efficient diffusion across their thin walls. This is where oxygen and carbon dioxide are exchanged, as well as where nutrients are delivered to cells and waste products are collected for removal.

While capillaries do connect arteries and veins, their main role is not simply as connectors; they are specifically designed for exchange. They also do not transport blood quickly, as that is a function characteristic of larger vessels like arteries and veins. Similarly, they do not pump blood; that function is managed by the heart. Therefore, the emphasis on the exchange process accurately represents the critical role capillaries play in the circulatory system.