Question

the human cardiovascular system is considered closed because ____________. a. blood is continuously circulated in the body. b. blood provides nutrients to organs. c. blood collects oxygen from the lungs d. there are no holes for blood to enter or leave the system please select the best answer from the choices provided.

Explanation:

A closed - circulatory system means that blood is contained within vessels and does not leave the system. Options A, B, and C describe functions of blood but not why the system is closed. Option D correctly states that there are no holes for blood to enter or leave the system, which is the characteristic of a closed - circulatory system.

Answer:

D. there are no holes for blood to enter or leave the system