It is said that the new teacher was once a policeman.

It is said that the new teacher was once a policeman.
Yes.He_____a policeman for 6 yearsbefore,he_____a PE teacher two years ago.
A.had been;became B.hasbeen;became C.has been;becomes D.was;had become
选项和理由
顺便告诉我过去完成时和现在完成时的区别,