I'll go to the library as soon as I finish what I .
A. was doing
B. am doing
C. have done
D. had been doing
网友回答
A. was doing
(答案→)B. am doing
C. have done
D. had been doing
解析：考查时态。句意：我一完成作者做的事情，就去图书馆。过去进行时指过去某一时刻正在发生的事情，排除A；C表完成，排除C；过去完成时指“过去的过去”，这里没有明显的过去的动作，排除D；故选B。