按要求完成下列各句。
1. The man is talking with a lady.  He gave us a talk last week.(合并为一句)
    The man _______ gave us a talk last week _______ _______ with a lady,
2. Whatever he says, I don't believe him.(改为同义句)
    _______ _______ What he says, I don't believe him.
3. My father often made me do a lot of homework at the weekends.(改为被动语态)
    I _______ _______ _______ _______ do a lot of homework at the weekends.
4. Stamps are used for sending letters.(对画线部分提问)
    _______ _______ stamps _______ for?
5. The train had left when I got to the train station.(改为同义句)
    The train had left _______ _______ _______  I got to the train station.