问题补充：
As we all know, smoking people’s health.
A. is harmful to
B. do harm fo
C. does harmful to
D. harm
答案：
(答案→)A. is harmful to
B. do harm fo
C. does harmful to
D. harm
解析：考查词组和主谓一致：对…有害：be harmful to或do harm to或用harm sth，所以先排除C项，当主语是动名词的时候，谓语是单数，选A。
