The teacher ____ the office for a few minutes when we arrived. We didn't meet him. [ ]

A. had left                    

B. had left    

C. has been away from        

D. had been away from    

砂浆按其用途可分为（）。

A.砌筑砂浆

B.抹面砂浆

C.装饰砂浆

D.防水砂浆