By the time he arrived in Beijing, we there for two days.
A. will have stayed
B. stay
C. have been staying
D. had stayed
网友回答
A. will have stayed
B. stay
C. have been staying
(答案→)D. had stayed
解析：考查时态。by the time用完成时态，根据arrive用过去时态，故用过去完成时，表动作先于发生。选D。