在更换或检查电动潜油泵井油追时，可以不管的闸门（）。 A.生产闸门 B.回压闸门 C

Not until they left school ____how much their teachers loved them and helped them.

A．that they realized

B．had they realized

C．when they would realize

D．did they realize

_____ endless tale of difference, Americans can still find many similarities between themselves.[ ]

A. In spite of  

B. Because of

C. As for  

D. In time of

反映经济的数量变化程度，通常是用()表示。

A．经济增长速度

B．经济增长率

C．经济发展速度

D．经济发展率

调速器的种类？

由毛细血管组成的结构是[ ]

A．肾单位

B．收集管

C．肾小球

D．肾小囊