对于一般工业和民用建筑工程而言，单位工程概算按其工程性质分为建筑工程概算和( )两大类。

A．一般土建工程概算

B．设备及安装工程概算

C．工器具及生产家具购置费用概算

D．弱电工程概算

If a vessel takes a sudden severe list or trim from an unknown cause, you should first（）.

A.determine the cause before taking countermeasures

B.assume the shift is due to off-center loading

C.counterflood on the side opposite the list or trim

D.assume the cause is environment forces