Answer:
B. Constants
Explanation:
Constants are the factors that stay the same throughout the entire experiment no matter which group. The definition of a constant is "a situation or state of affairs that does not change." this furthers the point that constant is the correct answer because they don't change in the experiment.
The answer is B,trust me I took the test.GOOD LUCK
These sorts of studies can help researchers determine the relative importance of nurture and nature in determining a trait. Nature here would refer to genetics passed down to an individual from its parents, whereas nurture refers to the environment the individual is exposed to.