Which of the following is NOT true about open and closed circulatory systems?

a. The open circulatory system of an insect does not transport oxygen to body cells; closed circulatory systems do.

b. A fish has an open circulatory system, land vertebrates have closed circulatory systems.

c. Both systems have some sort of a heart that pumps blood through the body.

d. The blood and interstitial fluid are separate in a closed system but indistinguishable in an open system.​