1. It started about two days ago. (对划线部分提问) 
                               it start?
2. You are not quiet. I think.（合成一句） 
    I                           that you              quiet.
3. Something is wrong with my stomach. (同义句转换)
    I have                           .
4. What's wrong with you? (同义句转换)
    What's                            with you?
5. improving, stressed out, I'm, my, English, because, isn't    (连词成句)