In a Study Described in Chapter 1, Psychologist Paul Solomon

In a study described in Chapter 1, psychologist Paul Solomon and his colleagues investigated the effects of the herb gingko biloba on memory, concentration, and other mental tasks. All participants in the study took a battery of tests at the beginning and end of the six-week study. The results showed that:

A) test scores increased about the same for the participants in the experimental group and for the participants in the placebo control group.
B) test scores actually decreased for the participants in the experimental group and increased slightly for the participants in the no-treatment control group.
C) test scores were virtually identical both times the participants were tested.
D) although test scores stayed about the same, participants in the study subjectively rated their memory and concentration as being significantly improved.