【正确答案】 C

【答案解析】[听力原文]
   W: Jim, thank goodness, you've arrived. The class presentation started half an hour ago and I was just beginning to panic.
   M: I am sorry. I'm late, Allen. This morning has been a real mess, and I didn't think I was going to make it here at all.
   W: Why are you late? Our whole presentation depends on these graphs you are holding.
   M: Yes, I know. I'll tell you about it later. First let's see how we are doing to time. Two groups are still ahead of us, aren't they? The presentation on the rights of the consumers and the analysis of the stock market. That means I've got about twenty minutes to sort out.
   W: You do look cold. What happened?
   M: I've been standing outside in Arctic temperature for over an hour waiting for a bus.
   W: Over an hour? But I thought your apartment was only a ten-minute bus ride to your campus.
   M: On normal conditions it is. But the bus was delayed because of the weather and when I stepped into a drugstore to call home for a ride, the bus went by. As luck would have it, there was no one at home, so I had to wait another forty-five minutes for the next bus.
   W: So sorry about what you experienced. Well, we still get twenty minutes to gather our wits together.
   M: We'd better stop talking; people are turning around and looking at us.
   What are the students doing when the man arrives in class?
四项均为现在分词，可能考查正在做某事；从选项中的exam、class discussion等可大致推断对话发生在学校。本题可能考查某人正在做某事，对话内容可能与学生相关。
   女士对男士说“你终于到了!课堂报告半个小时前就开始了，我已经开始恐慌了。”可见，同学们正在做课堂报告，故选C。