1. The headmaster saw the children playing on the playground. (变成复合句)
    The headmaster saw the children _________ _________ on the playground.
2. This volunteer work takes each of them several hours a week. (对划线部分提问) 
    _________ _________ does this volunteer work take each of them a week?
3. I'd like to help people who don't have home. (改为同义句)
    I'd like to help _________ _________.
4. Ming is a tenth grade student. He wants to be a professional singer. (合并句子)
    Ming is a tenth grade student _________ _________ to be a professional singer.
5. I want to be a volunteer because I think it is great. (合并成一个句子)
    _________ a volunteer _________ great.