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.
选C。
如选D的话,New drug is sold for three times the price ofdrug /product(但是后面不缺drug /product,实际上缺的是price). 而如果补全后面的the drug’s maker charges for another product,应该是:the drug’s maker charges price for another product。可以看到原文的the price就是定语从句的先行词,即用that引导的定语从句!
我选了E,但看了楼上andy的解释后觉得C正确。将句子第二部分还原成正常语序就会看得比较清楚:drug’s maker charges for another product with the same active ingredient $10(举个方便的例子).然后 $10 = the price = that.