加氢装置检修时，容器内可能含有的有毒有害气体有（）。
A、硫化氢
B、氨气
C、轻烃
D、氯化氢
参考答案：A, B, C
假如你是李明的母亲，请根据对话内容完成电话留言。(3分)
A: Hello. I’d like to speak to Li Ming.
B: Sorry. He isn’t in right now.
A: Oh. Can I leave a message?
B: Sure, go ahead.
A: This is Zhang Han speaking. Please tell him not to forget to take his camera tomorrow.
B: OK. Zhang Han . I’ll give him the message myself.
A: Thanks. Goodbye.
B: Bye.
一幅地图，底边长为24cm，比例尺为1：50000。现在把地图缩小，底边长为12cm。这幅地图缩小后比例尺为____________。
