法兰，人孔紧固螺栓时应采用（）扳手。
A.开口
B.活络
C.套筒
参考答案：C
As soon as the crew(船员) were attacked, the police _________to look into the matter.
A．set down
B．set out
C．set about
D．set up
以下不属于生物防治的是（）。
A.以虫治虫
B.以真菌治虫
C.以病毒治虫
D.人工诱杀
