What three features are common to all circulatory systems?

Question

This is quite broad and I’m not sure what to say.

Answer 1

A pressure gradient (e.g systole and diastole), a channel for the fluid to flow through(e.g blood vessels, airways) and a closed circuit( arteries to veins to heart to arteries)

Answer 2

I believe the right answer is:

1) Some sort of fluid that conveys gases and nutrients. Of course in humans this is blood, but in insects with simple circulatory systems this is hemolymph

2) Vessels in which the fluid is conveyed

3) A muscular organ that pumps the fluid - i.e. the heart.

It seems to me like you would need those three elements to have a proper circulatory system.