军第二届文艺汇演

硬聚录乙烯（PVC-U）管不适用于（）。

A.排污管道 

B.雨水管道 

C.中水管道 

D.饮用水管道 

Which values are NOT permitted to be part of the primary key

A．alpha-numeric characters

B．punctuation

C．special characters

D．NULL

一闭合线圈在匀强磁场中做匀角速转动，角速度为240π rad/min，当线圈平面转动至与磁场平行时，线圈的电动势为2.0 V。设线圈从垂直磁场瞬时开始计时，则该线圈电动势的瞬时表达式为__________________；电动势在s末的瞬时值为_________。

Kerry isn’t working hard to __________ his wife and children, which in my opinion will __________ his marriage failure.

A．bring up, add to

B．get hold of, lead to

C．provide for, contribute to

D．raise up, add up to

省煤器、减温器单独进行水压试验时工作负责人应先做哪些工作？