Question

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

Answer 1

A

试题分析：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。
点评：过去完成时一定要注意时间的起点，它不是的是过去的过去，要找到时间的参照点。