Question

multiple choice question
the _ are the upper, thin - walled chambers of the heart.
o atria
o ventricles
o aorta
o veins

Explanation:

The heart has four chambers. The atria are the upper chambers with thin walls. Ventricles are the lower chambers with thick walls. The aorta is a large artery. Veins are blood vessels that carry blood to the heart.

Answer:

atria