Question Detail
Question
Blood returns to the heart without leaving this system of tubes, and because the blood remains within this closed system, we refer to vertebrate circulation as a ______.
Correct Answer
Option C is the correct answer.
Detailed Explanation
In a closed circulatory system, blood is contained entirely within blood vessels and never directly bathes the organs. This is characteristic of all vertebrates. In an open circulatory system, blood (hemolymph) flows into open spaces (sinuses) surrounding the organs.
Hint
The key phrase is 'blood remains within this closed system'.