A study of the effect of caffeine on muscle metabolism used eighteen male volunteers who each underwent arm exercise tests. Nine of the men were randomly selected to take a capsule containing pure caffeine one hour before the test. The other men received a placebo capsule. During each exercise, the subject's respiratory exchange ratio (RER) was measured. The question of interest to the experimenter was whether, on average, caffeine changes RER. Which type of t-test should be used in this situation?

*note: RER is the ratio of CO2produced to O2consumed and is an indicator of whether energy is being obtained from carbohydrates or fats.

Group of answer choices

A.) One Sample T-Test

B.) Independent Samples T-Test

C.) None of the T-Tests would be suitable

D.) Paired Sample T-Test