【正确答案】
C
【答案解析】[听力原文] 23-25
M: How did you like yesterday's astronomy class?
W: It was interesting. But the point she was trying to make seemed a little far-fetched.
M: Oh, that new theory that ocean water came from comets?
W: Yeah. Do you remember what it was based on?
M: Some recent satellite photos, I think. Apparently, Space satellites recently detected thousands of small comets colliding with earth's outer atmosphere, almost 40,000 per day.
W: OK, they're collided with atmosphere. So that's what created the water?
M: It's not the collision that created water. Comets contain water. They're made up mostly of cosmic dust and water. When they collide with the atmosphere, they break up. And the water they contain rains down to earth. Ocean water came from that rain.
W: Oh well, this morning I asked my geology professor about that. He said that most geologists don't accept it.
M: Why not?
W: Special research indicates that most of the water molecules from the comet would have burned up as they fell through the atmosphere. Enough rain couldn't have reached the earth to fill up the ocean.
M: Well, did the geologists have an alternative theory to explain where ocean water came from?
W: Yeah, he said the more traditional view is that the ocean water came from volcanoes.
M: From volcanoes?
W: Right. They say volcanic fumes are mostly steam. And they claimed that it was the volcanic steam that created the oceans, not rain from comets.
23. What are the speakers mainly discussing?
综合推断题。男士在对话开始时提到了海水来自彗星这一新理论，接下来的对话主要就是围绕该理论展开的，最后还引出了海水来自火山这一传统理论，由此推断，对话主要与地球上水的来源，特别是海水的来源有关，故选C。
【正确答案】
D
【答案解析】[听力原文]
What aspect of volcanoes does the woman mention?
信息明示题。女士指出，地质学者认为火山气体大多为蒸汽，故选D。
[考点] fill sth. up 意为“填写，填满，充满”，与fill 相关的短语还有：fill sb.'s shoes 接替某人的工作、职务等；fill in (for sb.)临时接替某人；fill sth. in 除了指“填写，补充，填满”以外，还可指“打发，消磨(时间)”，如： Jack filled in the afternoon watching television．杰克看电视以打发下午的时间。