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. a b c d

Explanation:

To determine why the human cardiovascular system is closed, we analyze each option:

• Option A: Continuous circulation (A) is a feature of the system but not the reason it's "closed."
• Option B: Providing nutrients (B) is a function of blood, not related to the system being closed.
• Option C: Collecting oxygen (C) is part of gas exchange, not related to the system's closed nature.
• Option D: A closed system in biology (for the cardiovascular system) means blood stays within vessels/heart with no openings for entry/exit. So D correctly defines why it's closed.

Answer:

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