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：考查时态。句意：当老人开始走回家的时候，太阳已经下山了。说明太阳下山是在老人回家之前。老人回家用过去时，太阳下山用过去完成时。这两句的时态要一致，故A正确。