Independent: The second group is not given the drug.
Dependent: Dr. Smith wants to examine weather a new drug increases the maze running performance of older rats.
Constants: Dr. Smith teaches two groups of older rats to find a piece of tasty rat chow in the maze.
Answer:five types of bones in the skeleton: flat, long, short, irregular, and sesamoid.
Explanation:
I believe it is DNA: deoxyribonucleic acid
