用所给动词的适当形式填空。
1. His father stopped ________ (work) because of his illness.
2. Mary often helps her moth _______ (do) the housework after school.
3. Project Hope _______ (train) many teachers so far.
4. He _______ (listen) to music when we called him that evening.
5. We _______ (learn) two thousand English words in the last four years.
6. My old grandfather has come here _______ (take) his bag back.
7. There is a group of children _______ (play) football on the playground.