Both. You can use it as singular or plural.
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Answer: A
Explanation: the taking the quiz
Answer:
Regulate heat throughout it's body,
Explanation:
Countercurrent Heat Exchange is a normal and varied mechanism in organisms that utilizes parallel pipes of flowing fluid in opposite directions in order to save energy, such as blood flow. For example, a whale's tongue uses this system through the blood flow to the tip of the tongue, where the countercurrent heat exchange system heats up blood returning to the body.
