什么是间隙密封
参考答案：间隙密封是依靠相对运动零件配合间的微小间隙来实现密封的。
Without this year’s Nobel Prize in physics winner Charles Kao’s idea of fibrotic（光纤的）communications, the “modern” telephone and Internet _________impossible．
A．will be
B．were to be
C．should be
D．would be
There is a bank ______ Center Street. [ ]
A. on
B. between
C. across from
D. in front of
