它是动词,但又不能作谓语.可以作主语、表语、宾语、定语、状语、宾补. 它的形式有:to do /doing 1. To dong morning exercises is important.(主语) 2. My ambition is to be a teacher.(表语) 3. I saw him coming. / enter the room.(宾补) 4. I enjoy watching TV.(宾语) 5. I come here to see you.(状语) 6. I want something to eat.(定语) 看看能否有帮助.