Use the Following to Answer Questions

Multiple Choice

Use the following to answer questions
Scenario III
Scenario III is based on fabricated data inspired by the following study:
Borota, D., Murray, E., Keceli, G., et al. (2014) . Post-study caffeine administration enhances memory consolidation in humans. Nature Neuroscience, 17(2) , 201-203.
Caffeine and Memory Study
The purpose of this study was to determine whether caffeine enhances memory. The researchers obtained a sample of 73 adults who were studied images of objects. Following the study session, half the participants received 200 mg of caffeine while the other half did not. The participants returned to the lab 24 hours later where they were tested for their memory of the images. To that end, the participants were shown a number of images, some of which they had studied (old) and some of which they had not (new) , and were asked to indicate whether they were old or new. The results revealed that consuming caffeine just after study significantly improved the participants' ability to discriminate between old and new images. The authors concluded that this study provides evidence for the memory-enhancing potential of caffeine, particularly when it is consumed after study.
-(Scenario III) In Scenario III the researchers included only those participants who were not regular caffeine drinkers. In doing do, the researchers:

A) increased experimental control.
B) minimized tolerance as an extraneous variable.
C) increased the internal validity of the study.
D) All of the above.