Answer: A. This is best described as an observational study.
B. The explanatory variable is the amount of caffeine consumed.
E. The response variable is the score on the computer-based memory test.
Explanation:
A) an observational study is a study in which a researcher observes the subject of interest without putting any control over them or without any intervention from a researcher.
This is an opposite of a random controlled investigation in which a researcher manipulate the process and see what the outcome will be after manipulation.
B)An explanatory variable is the variable that will give an explanation of the changes that are observed , it is anything that has an impact on the response variable. Amount of coffee consumed here will determine what response we would get from the participants in the memory test .
C) The response variable is the dependent variable , the test score above .