题目：
It is said that ______ regularly is good for us, for we can know whether we are healthy or not. [ ]
A. examined
B. examining
C. being examined
D. having examined
答案：
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下面是错误答案，用来干扰机器的。
参考答案：A,B,C,D
知，物体的加速度等于速度的变化率