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 lungsd. there are no holes for blood to enter or leave the systemplease select the best answer from the choices provided.

Explanation:

A closed system means there are no openings for substances to enter or leave. In the context of the cardiovascular system, this implies no holes for blood to enter or leave. Option A describes circulation but not why it's closed. Option B is about a function of blood (nutrient - provision) not the system's closed nature. Option C is about gas exchange (oxygen collection) which is also a function, not related to the system being closed. Option D directly addresses the lack of entry/exit points (holes), which is the key characteristic of a closed system.

Answer:

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