—Can you tell me_____?        

—Sure. Two years ago.      [ ]

A. when did they build the new teaching building        

B. when they build the new teaching building        

C. when they built the new teaching building        

D. when they are building the new teaching building

最近，你单位每天都要加班，恰逢此时你的父亲病重，你怎么办？