Which statement is true regarding ventricles? a. they supply only unpurified blood. b. they're the top chambers of the heart that supply purified blood to other parts of the body. c. they're the bottom chambers of the heart that supply purified blood to other parts of the body. d. they're smaller than atria.

The correct option is C.
The human heart is divided into four chambers that are separated by valves. The upper two layers of the heart are called atria. The lower two chambers of the heart are called ventricles; we have the right ventricle and the left ventricle. The ventricles pump blood from the heart to the body. 

Ventricles are found at the bottom psrt of the heart. The heart is divided into four chambers. So the answer to your question is They're the bottom chambers of the heart that supply purified blood to other parts of the body. So this is the third option or letter C.

They might be white heads, basically pimples but you should ask your parents to check them out before it’s something bad.

D. contract and relax