当采用卷材或板材时，绝热层材料应表面平整，其允许偏差为（）mm。

A、5

B、10

C、15

D、20

—What did the policeman say to you just now?

—He asked ______ when the accident happened. [ ]

A. what I was doing

B. what was I doing

C. what I am doing

D. what am I doing