书名：全新制怪物讲师教学团队的TOEIC多益阅读1,200题全真模拟试题
页数：p.38第124题
题目：
Staff members agreed to work extended hours and to treat patients from 6
A.M. until ______ midnight.
(A)approximate
(B)approximated
(C)approximately
(D)approximating
疑问：答案是C，但midnight是名词，为什么不是用A形容词修饰?