铣床进给箱快进和工作进给的互锁性能不可靠，会造成正常进给时突然跑（）速的故障。
A、较快
B、快
C、较慢
D、慢
参考答案：B
Good use___ the natural resources to improve people’s life in this area．
A．has been made of
B．has made of
C．has made
D．has been made
Don’t argue with him any longer. You are only wasting your breath （） to win him over to your side.
A. having tried
B. to try
C. to be tried
D. trying
