离心泵启动时不必将泵壳内充满水。
参考答案:错
Only one third of the people present at the meeting voted ______ the new law.
A.in search of
B.in favor of
C.in short of
D.in case of
在梯子上工作时,梯与地面的斜角度应为()度左右。
A、40-45
B、50-55
C、60-75
D、70-75