One of our rules is that every student    wear school uniform while at school.

A．shall

B．could

C．might

D．will

泵是化学工业等流程工业运行中的主要流体机械，毒性或腐蚀性较强的溶液可选用( )。

A．齿轮泵

B．屏蔽泵

C．离心泵

D．螺杆泵