51. An open circulatory system differs from a closed one in that:
(A) The open circulatory system has a combination of blood vessels and large thin-walled sinuses whereas a closedcirculatory system has only vessels.
(B) An open circulatory system opens into the heart whereas the closed circulatory system does not.
(C) An open circulatory system opens into arteries and is drained by veins whereas in a closed one it is just the reverse.
(D) An open circulatory system drains into the mantle cavity whereas a closed circulatory system drains into thehemolymph.
(E) A closed circulatory system is completely encased in the body cavity whereas the open one is not.