– What a heavy rain!

– So it is. We have to delay ______ the sports meeting until it is fine.

A．to hold

B．holding

C．held

D．being held

氯化消毒时，需氯量等于（）

A.加氯量-余氯

B.加氯量-有效氯

C.加氯量+有效氯

D.加氯量+余氯

E.以上都不是