Read the dialogue and answer the question. P: Good afternoon! What can I do for you? S: I’d like to make a complaint. It’s so hot on the train. There seems to be something wrong with the air-conditioning. P: Could you tell me which train did you take? S: The train in Line 1 pulled in Qingniandajie Station at about 15:10. P: All right. We’ll inform the Maintenance Department the problem immediately. They’ll get here to check it as soon as possible. Question: What is the dialogue talking about?