问题:
[单选题]
How does exercise sharpen the mind according to Para. 2?
A.
By increasing the brain size.
B.
By decreasing the protein level.
C.
By extending the time of concentration.
D.
By strengthening brain cells’ connections
试题来源参考:成人高考专升本,英语真题试卷,英语答案,英语历年真题,英语模拟试卷,成人高考专升本入学考试