GWD4-Q4，题目太傻没人问？twice that是什么？

Q18: GWD4-Q4

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
        

选C

我已经看过关于twice用法的大帖子http://forum.chasedream.com/dispbbs.asp?boardid=23&replyid=244377&id=31796&page=1&skin=0&Star=1

并知道倍数（twice）的基本用法：

i. x times(twice) + the + n.

ii. x times adj. (比较形式) than

iii. x times as adj. as 注意里面的adj要和前面的名词匹配

A do x times as adj. … x as B do

iv. x times + what 分句

问题是：上面这道题中的twice算是什么用法？twice that? 或者这个that是什么从句？  迷茫……

谢谢过路人的解答！

不对啊，如果是定语从句的说法的话，按照OG，如果是that修饰必须要紧跟在修饰词后面的啊，而且不能有逗号才对？？