单项选择题 可用于测定寡聚蛋白质的分子量，而（）可用于测定寡聚蛋白质各个亚基的分（）子量。

单项选择题 You are about to enter a compartment to investigate a suspected smoldering fireIf youre not wearing a self-contained breathing apparatus, you should test the compartments atmosphere to determine if there is/are （）.

问答题 什么是服务期望，包括哪几个种类？