硅酸盐尘肺中危害最大的是
A.滑石肺
B.云母肺
C.石棉肺
D.石墨肺
E.水泥肺
参考答案:C
小华在学习了“声音是什么”以后,总结出以下四点.其中你认为错误的是 [ ]
A.声音是靠物体的振动产生的
B.声音以波的形式传播
C.振动停止以后,声音要慢慢消失
D.声具有能量
Hurry up, Jack. We have to get to the station before 11:45 ________ we can catch the 12:00 train. [ ]
A. since
B. after
C. as soon as
D. so that