Use the Following to Answer Questions

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) The researchers who conducted the study described in Scenario III were able to make a causal statement about the effect of caffeine on memory because:

A) they conducted their study in a laboratory setting.
B) they examined memory in only those who were naïve to caffeine.
C) they randomly assigned participants to treatment conditions and controlled how much caffeine each condition received.
D) they performed an independent t-test.