_______ are the first group of invertebrates which have developed a closed circulatory system.
Correct answer: B. Annelids
- A. Nematods
- B. Annelids
- C. Arthropods
- D. Molluscs
Explanation
Annelids are regarded as the first major invertebrate group with a closed circulatory system, in which blood remains within vessels. Arthropods have an open circulatory system, so students who associate greater structural complexity with closed circulation may choose c.
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