Q8:
A new hair-growing drug is being sold for three times the price, per milligram, as the drug’s maker charges for another product with the same active ingredient.

A.        as
B.        than
C.        that
D.        of what
E.        at which
   Answer:

请问大家一下,道题为什么选D呢?感觉"of what"和charge搭配不对啊.谢谢~