Open VS closed circulatory system

Question

What differentiates a closed circulatory system from an open circulatory system?

a) the presence of vessels

b) the presence of a heart

c) direct contact of circulating fluid with tissues

d) the presence of a circulating fluid

I believe option c) is the correct answer but im not sure, can someone please confirm it?

Answer 1

In a open circulatory system, blood is pumped from the heart into body cavity allowing blood to bathe the tissue and then return to heart. However in closed circulatory system there is a continuous system of vessels and is not pumped into body cavities.

The question what differentiates a CLOSED circulatory from a open system. Therefore, it is option (A) the presence of vessels.

If the question was what differentiates a open circulatory system from a closed system, then option (C) would be correct.

Thank you!