Most arthropods and some mollusks and tunicates have _____ circulatory systems, which means fluid transporting nutrients and oxygen flows directly into internal organs.
A. closed
B. nonexistent
C. open
Answer (2)
Arthropoda and molluscs have open circulatory systems - meaning haemolymph (Their equivalent to blood) directly bathes the tissue, and isn't enclosed in blood vessels, as seen in a closed blood system, as in humans for example.
Most arthropods, as well as some mollusks and tunicates, have open circulatory systems. In these systems, hemolymph flows directly into internal organs, rather than being confined to blood vessels. Thus, the correct answer is C. open.
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