1.Hello!May I speak to Bob?-Sorry,but he ----- for a month.

1.Hello!May I speak to Bob?-Sorry,but he _____ for a month.A.had been away B.was left C.left D.has been away2.I ______ him since I began to live in the city,A.know B.have known C.knew D,will konw3.She _____ already ______ in this school for two years.A.was;studying B.will;study C.has;studied D.are;studying4._____ he came to study in the university.he has made much progress.A.While B.When C.Since D.After