单选题
{{I}} Questions 11-13 are based on the following conversation. You now have 15 seconds to read the questions 11-13.{{/I}}
单选题
What is the main topic of the conversation?
【正确答案】
A
【答案解析】[听力原文]Questions 11-13
W: Did you hear the thunder last night?
M: Did I? It was really loud.
W: I didn't see any lightning though. I thought that thunder and lightning always occur together.
M: They do. It's not possible to have one without the other since thunder is a direct result of lightning.
W: Really?
M: Yes. Thunder is produced by the rapid expansion and contraction of highly heated air along the path of an electrical discharge.
W: In other words, lightning quickly heats the air and causes thunder. But if the lightning is there, why can't we see it?
M: Because it sometimes occurs very high in the clouds.
W: I wonder whether it's possible to see the lightning and not to hear the thunder.
M: Yes. It's possible if the lightning flashes are far enough away. Sound doesn't travel as far as light.
单选题
What led to the conversation?
【正确答案】
A
【答案解析】
单选题
According to the conversation, where does thunder occur?