气相色谱法中选择载气的流速和种类时，应该______。
   A．载气的流速大小与载气种类的选择无关
   B．流速小，选择相对分子质量小的载气
   C．流速大，选择相对分子质量大的载气
   D．流速小，选择相对分子质量大的载气

The story of the boy’s walking on the stones shows that（）.

A．he wished to solve his problem
B．he wanted to get his father killed
C．he wished that his father could help him
D．he was emotionally tolerated and had gone crazy

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It was until dark ______ he found ______ it was the correct way to solve the problem. A) that; what B) that; that C) when; what D) when; that 点击查看答案