按照要求完成句子。 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.