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2)Since when did you start to work?
3)George has been the best student since he has entered the University
4)The children have changed a lot in the last time
5)Mr. Brown hasn t been at work for last week

2) When did you start to work? 3) George has been the best student since he entered the University 4) The children have changed a lot recently. 5) Mr. Brown wasn't at work last week