题目选项分析

Of the 60 participants in a clinical trial, 30 participants were considered to be in the experimental group, and were administered a large dose of an experimental painkiller called nexaphedrinol, while the 30 remaining participants were considered to be in the control group, and were administered the same dose of a placebo. Afterward, participants in the experimental group exhibited fine motor skills that were more diminished than those of the control group. The observed detrimental effects on fine motor skills were attributed to a compound in nexaphedrinol called phedrine, which temporarily damages nerve endings.

Which of the following, if true, would best support the conclusion that a certain compound in the painkiller was responsible for the observed results?

【选项】Phedrine is a relatively ubiquitous compound found in a variety of medicines, some of which may have been taken by the participants in the experiment.