The circulatory, or cardiovascular system, is composed of
a. heart, arteries and veins.
b. lungs, heart and brain.
c. heart, blood and blood vessels.
d. lungs, blood vessels and heart.

The circulatory system is composed of blood vessels that take blood apart from and towards the heart. Arteries move blood aside from the heart and veins bring blood back to the heart. The circulatory system offers oxygen, nutrients, and hormones to cells, and eliminates decay products, like carbon dioxide.

a- multicellular

b-eukaryotic

c-no cell wall

d-heterotrophic

e-autotrophic