I went to shanghai last week,      I visited the World Expo.

A．When

B．Where

C．Which

D．that

对于要求自控的变水量空调水系统,在风机盘管的供水管上应设置下列哪种阀门?

A.三通电动阀

B.两通电动阀

C.恒温阀

D.手动调节阀