I believe the correct answer is B: The prevention of second-hand smoke. Hope this helped!
-TTL
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.
The answer should be around 70%!
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A higher fat percentage than muscle percentage.</span>
