
Passage: In one study, 51 volunteers from middle school students were divided into a test group and a control group and trained in the same math skills. During the five-day training, the researchers used a technique called transcranial random noise stimulation to deliver mild shocks to areas of the brain thought to be related to computing power in 25 members of the test group. The results of subsequent tests showed that the ability to perform mathematical operations of the members of the test group was significantly higher than that of the control group. To their surprise, the improvement of this ability can last at least half a year. As a result, the researchers believe that to deliver mild shocks in the brain can improve the brain's ability to calculate.
Question: Which of the followings, if true, best supports the above view of the researchers?
A. A.This kind of non-invasive stimulation is cheap and will not bring any pain to the human body.
B. B.After delivering mild shocks to the brain, the blood flow between neurons in the brain increased significantly, but returned to normal after repeated stimulation.
C. C.Before the experiment, the math scores of the two groups were about the same.
D. D.Subjects with delivering mild shocks to the brain were more concerned about their behavior and were more focused during the test.
Answer: