能保证准确瞬时传动比的机械传动有（）。
A.螺旋传动
B.带传动
C.链传动
D.齿轮传动
E.蜗杆传动
参考答案：D, E
The calculations, had they been done by hand, ______all practical value by the time they were finished.
A．had lost
B．would lose
C．should have lost
D．would have lost
建设工程项目全过程质量控制的关键环节是( )。
A．设计质量控制
B．施工质量控制
C．决策质量控制
D．设备质量控制
