— What great trouble I have solving this problem now！   

—_____ my advice, you ________less trouble.

A．If you had taken, would have had

B．If you took, would have

C．If you had taken, would have

D．If you take, will have

微库仑法测定水中AOX时，当第二根吸附柱的测定值不大于一根吸附柱测定值的30％，就认为吸附完全，否则需将水样稀释。