带传动的优点是（）。A、效率高 B、传动平稳 C、易改变中心距 D、成本低 E、起保

He was busy writing a story, only ______ once in a while to smoke a cigarette.

A．to stop

B．stopping

C．to have stopped

D．having stopped

The other day, my father drove his car at ____ I thought was a dangerous speed. [      ]

A. as

B. that

C. which

D. what

塔中站是指基站机房为框架结构，包含在铁塔的四角之内。机房建筑物基础内的钢筋和铁塔地网应互连，并在铁塔四角外设环形接地装置，三者共同作为接地装置，接地网的面积应不小于（）。

A.15m*15m

B.5m*5m

C.10m*10m

D.25m*25m

提示承兑的性质有哪些