What vessel play a key role in regulating blood flow into capillaries?

The correct answer is Arterioles.

Explanation:

Arterioles are small arteries that branch off from larger arteries and lead into capillaries. They play a key role in regulating blood flow into capillaries by constricting or dilating in response to various factors such as tissue demand for oxygen and nutrients, blood pressure, and hormonal signals. By controlling the diameter of arterioles, the body can adjust the amount of blood flow to different tissues and organs as needed.