下列泵（）在启动时，必须先开出口阀。
A、计量泵
B、离心泵
C、磁力泵
D、屏蔽泵
参考答案：A
How much did the computer _____ you? And how much time do you _____ on it every day? [ ]
A. take; cost
B. spend; pay
C. cost; spend
D. pay; take
某振冲碎石桩，桩径0.6m，正方形布桩，桩距1.5m，处理后桩间土fak=100kPa，计算复合地基承载力特征值接近（）（桩土应力比n=3）。
A.110kPa
B.125kPa
C.145kPa
D.160kPa
