阅读下面对话，从方框内7个选项中选择5个恰当的句子完成此对话，并将其序号填入题前括号内。 A: Do you want to come here? B: Maybe man will go to live on mars in the future. C: But now it is a big step for man. D: Can man go to live on it? E: It will be more crowded. F: It is good for me. G: What is your unreal dream? A: What's your dream? B: I have an unreal dream. A: 1. B: I hope to be a Mars citizen (市民). A: It is perhaps, a true dream. B: 2. A: I see, there are so many people on such a small earth. It is too crowded everywhere. B: There will be more babies born this century on our planet. A: 3. B: So I hope to be a citizen who lives on Mars. A: It is a good idea to solve the crowded problem of our planet. B: 4. A: The scientist said that there is no air, no water and no life on it. 5. B: I don't think so, but I am sure man's dream to live on Mars will come true one day. A: Perhaps our dream will come true before long.