对话中， Susan说自己要乘飞机旅行， 而Angus说“that's great but it's scary how much pollution planes produce” ， 即他们在讨论是否应该选择坐飞机。 因此答案选 A 。

【听力原文】
F: Hi, Angus! I've just booked a weekend trip to London. It only costs ￡ 100, including airport tax! Much cheaper than the train! ...What's the matter?
M: Well, Susan, that's great but it's scary how much pollution planes produce.
F: Oh no, don't start about the environment again, Angus. Cheap air travel means people can see new places. Travel broadens the mind and all that...and London, Angus! I've wanted to go them for ages!