4-硝基邻二甲苯的熔点和比重分别是多少？

It was not until dark _____ he found _____ he thought was the correct way to solve the problem. [ ]

A. that; what

B. that; that

C. when; what

D. when; that

什么是糖化？

简述光盘文件的类型。

简述历史教学评价的功能。