---Oh, it’s five o’clock alreay. I must be going.----______?

A．Can't you stay a little longer

B．What’s this

C．Why are you

D．Do you sit here

测定酱菜中NaCl所用的标准溶液是（）

A.NaOH

B.HCl

C.Na₂CO₃

D.AgNO₃