When the old man to walk back to his house, the sun itself behind the mountain.
A. started; had already hidden
B. was starting; hid
C. had started; had already hidden
D. had started; was hiding
网友回答
(答案→)A. started; had already hidden
B. was starting; hid
C. had started; had already hidden
D. had started; was hiding
解析： 考察时态。句意：当老人开始走回自己的房子的时候，太阳已经躲在大山后面了。根据句意可知太阳落山是先发生的事情，然后老人才回家。要注意动词的先后关系，故A正确。