用所给动词的正确形式填空：
1. A cow _______ (eat) grass but gives milk.
2. The room is dirty. I _______ (clean) it in a minute.
3. Mary _______ (sing) three songs already. Let her have a rest.
4. It is late at night. Dad _______ still _______ (work) at the desk.
5. Tell Robert to turn off the lights before he _______ (go) out.
6. He put on his clothes and _______ (hurry) to school without breakfast.
