问题补充:
your composition carefully, some spelling mistakes can be avoided.
A. Having checked
B. Check
C. If you check
D. To check
答案:
A. Having checked
B. Check
(答案→)C. If you check
D. To check
解析:考查if引导的是从句,后面的就是主句,如果选B,那么前面的这个祈使句和后面的句子之间没有连词连接了,所以不能选B.