Question

max is testing how caffeine affects test scores. what might be a constant in this experiment?
the type of test the subjects are taking
the subjects favorite foods
the eye color of the subjects
all of these

Explanation:

In an experiment testing how caffeine affects test - scores, variables like favorite foods and eye color are irrelevant to the relationship between caffeine and test - scores. Also, to accurately measure the impact of caffeine on scores, the type of test should remain the same. So all these can be constants.

Answer:

D. All of these