问题补充:
We all know that doing morning exercises .
A. is good for our healthy
B. are good for our healthy
C. are good for our health
D. is good for our health
答案:
A. is good for our healthy
B. are good for our healthy
C. are good for our health
(答案→)D. is good for our health
解析:for后面健康应为名词,抽象事物一般用单数形式,所以选D。