I believe it’s D, please correct me if I’m wrong
By he NIH trying a new drug to help reduce pain associated with sickle-cell anemia, it's an example of an "experiment".
An experiment involves a hypothesis (an educated guess as to what's going to happen) and trying out the hypothesis and finding the solution.
Answer:
Well I do not think it would be A or B. The best answer I can give you is D. If you talk to someone face to face it makes the message more clear and the person will be able to understand better, plus it's another good way to give a message rather then mailing or something like that. If the answer is not D however then it would be C.
Explanation:
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Smooth and skeletal is the answer yuh