A、He had to attend Prof. Smith’s lecture. B、He had to go to see the dentist. C、He had to wait for an emergency call. D、He had to

M: Hi, Sue. I was wondering if you could fill me in on Monday’s class. I had to go to the dentist for an emergency and I missed Prof. Smith’s lecture. What was it on?
W: It was pretty interesting. She talked about volcanoes, active volcanoes under the... uh... West Antarctic ice sheet.
M: There are active volcanoes under the ice?
W: Apparently so. She said they help protect the ice sheet and prevent melting. Flooding will be pretty bad if that ice melted, not only there but all over the world.
M: You lost me there. Volcanoes are hot. How can something hot prevent ice from melting?
W: Wait a minute. Let me check my notes. Yeah, here it is. Volcanic heat melts just enough ice to create a slippery surface on the bottom of the glacier. This water allows ice to flow out into the ocean, so the solid interior ice is protected from the ocean’s warmth. Does that make sense?
M: Sort of. You mean that because the ice is flowing out to the ocean, the warmer ocean water can’t flow in.
W: Exactly. And the ice that melts is constantly being replaced by snow. Prof. Smith said that if the ice sheet ever broke up and melted, the sea level would go up 7 meters. Then we would have those floods.
M: Is that really possible? Or is it one of those exaggerations you hear all the time?
W: As far as I can understand, it is possible, because of the global warming. I mean, if the ocean got a lot warmer, that interior ice would be very likely to melt.
M: Thanks for telling me about the lecture. Sounds like I’ve missed a pretty important class.
22. Why did the man ask the woman about the lecture?
23. What did Prof. Smith say about active volcanoes under the West Antarctic ice sheet?
24. What can be inferred about the woman?
25. According to Prof. Smith, what will happen if the ice sheet melts?