It’s the duty of the police to ______ the public order.
Yesterday if the policeman _______earlier, the fight between the two boys would have been prevented.
I ______ Wang Tao in the street yesterday. We _______ each other since he went to Beijing.
Hardly ______ off the bus when ______ an old friend who he hadn’t seen for years.
---Where did you meet him?---It was in the hotel ______ he stayed ______ I met him.
The foreign visitors couldn’t help ________ by the beautiful scenery of the Great Wall.