一、单句填空
1.They (quarrel) all the morning.
答案have been quarrelling
2.I (prepare) for my birthday party.
答案have been preparing
3.He (listen to) the English program since he came to the U.S.,so he has made great progress.
答案has been listening to
4.The waiter (run) from this table to that table all the time.
答案has been running
