“O”形密封圈常被安装在()槽中或有倒角处。
A.矩形
B.正方形
C.梯形
D.三角形
参考答案:A
When _______ about their opinion of the effect of modern equipment on their performance of tasks, many young people gave a positive response.
A.asked
B.asking
C.being asked
D.to ask
如图所示是一只白炽灯的效率图,根据此图可以知道转化成的内能为_____J ,白炽灯的效率为_____ 。