选词填空：根据对话内容，用方框中所给单词的适当形式填空，每词限用一次。

water    no    Earth    it    for

Bill: I saw a great programme on TV about space yesterday evening.
Tony: What is   小题1:   about?  
Bill: Scientists have discovered   小题2:    on Mars.
Tony: Really? That’s very fantastic. Have they discovered life on Mars?
Bill: Well, they’re looking   小题3:   life but they haven’t found anything yet.
Tony: I know there’s   小题4:   life on the moon.
Bill: Yes, that’s right. So far there’s only life on  小题5:   .
Tony: Are we alone with so many stars in the universe?
Bill: I am interested in it, so I want to be a scientist when I grow up.
Tony: I wish you will.