Which of the following organisms has a closed circulatory system?

a. Sponges

b. Cnidarians

c. Nematodes

d. Insects

e. Vertebrates

The correct answer is E. Vertebrates have a closed circulatory system.

Explanation:

The main mission of the circulatory system is to deliver oxygen and nutrients to all body cells.

In the closed circulatory system, blood travels inside a network of blood vessels, without leaving them. The material transported by the blood reaches the tissues through diffusion. It is characteristic of all vertebrates, including humans.