— Lucy looks blue today.

— Yes, but I don't know what it is________makes herso upset. [ ]

A. as

B. what

C. that

D. which

发生人员触电事故时，应立即（），使触电者迅速脱离电源。

A.关闭电源开关

B.用手将触电者拖离

C.用金属棒挑开电源线