求助各位大牛们ＧＷＤ－４－４还是不会啊！！

Q18: GWD-4-4

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.

1. as

2. than

3. that

4. of what

5. at which
                   

为什么不可以选Ｅ呢？相当与是the drug’s maker charges for another product with the same active ingredient　at　 the price．

这样不可以吗？

OG上面将which要满足就近指代原则..

这里面明显前面还有个milligram啊.