右图是1865年4月制成的轮船“黄鹄”号(复原图)。它的诞生标志着(  )

在生产和生活中，人们常把密度作为所选材料的主要考虑因素，下面属于主要从密度的角度考虑选材的是（　　）

汽车在紧急刹车时，总是滑行一段距离才能停下来，这是由于____ ；当雨天路面有水时，轮胎与地面间的摩擦会变____ ，汽车在紧急刹车后滑行的距离将比路面没有水时____ 。因此，司机驾车要注意：“雨天路滑，小心慢行”。

根据句意及所给的汉语，补全所缺的单词，每空限填一词。
____ The girl often helps me with my __________（最糟糕的）subject.
____ I think you made a good _________（决定）.
____ We looked at each other in _________（沉默）.
____ I had an unusual           (经历) last Sunday.
____ You shouldn’t _________ (播放) your CDs too loudly.
____ Now many students are under too much __________（压力）.
____ If Paul _________（失败）the exam again, his teacher will talk with his parents about it.
____ He had an accident. But ___________（幸运地）, he was not badly hurt.
____ It is very __________（危险的）to play football in the street.
____ He didn’t know what was __________（发生）outside.