用含有at的词组填空：1（）,after hours of climbing,we reached the top of the mountain.
接上：2.You used to live in London,didn’t you?Where are you living （）?
3.Most of the time Pat is a very nice person,but （）he can be very unpleasant.
4.（）the police thought they had the right man,but later they realized their mistake.
5.There must have been （） 2,000 people at the concert.
6.Doctor,my son has had a serious accident.Can you come （）?