【多选题】专性厌氧菌在有氧环境中不能生长的原因有( )。
【简答题】若a=1- 2 ,先化简再求 a 2 -1 a 2 +a + a 2 -2a+1 a 2 -a 的值.
【单选题】听力原文:W: What size do you wear? M: A twelve. W: Oh, you're lucky. I have just the right size in store. Here it is. Why don't you try it on? Where does the conversation probably take place?
【单选题】化简 a+1 a 2 -a ÷ a 2 -1 a 2 -2a+1 的结果是( )