－Congratulations to you! I hear you got the first in the English Speech Competition.

－__________.

A．Don’t mention it. I think that is only my past.

B．Thanks. But I think I could have done better.

C．There is nothing to cheer for.

D．No, no. it’s a piece of cake.

乳化液用水的PH值是（）以下时的水应经过适当的处理方可使用。