Doctors say that exercise is important for health but it must be exercise.A. frequentB. n

问题补充：

Doctors say that exercise is important for health, but it must be exercise.

A. frequent

B. normal

C. regular

D. usual

答案：

A. frequent

B. normal

(答案→)C. regular

D. usual

解析：词义辨析题。A．frequent 频繁的 B．normal 正常的 C．regular 有规律的D．usual 通常的句意：医生说锻炼对健康很重要但是必须是有规律的运动。 根据语意选C