When the old man to walk back to his house, the sun itself behind the mountain.
A. started; had already hidden
B. had started; had already hidden
C. had started; was hiding
D. was starting; hid
网友回答
(答案→)A. started; had already hidden
B. had started; had already hidden
C. had started; was hiding
D. was starting; hid
解析：老人开始跑回家与太阳落山两个动作都发生在过去，而后者又发生在前者之前，故前者用一般过去时，后者用过去完成时。