jack __into the house when no one___

问题描述:

jack __into the house when no one___
A slipped ; was looking
B had slipped ; looked
C slipped ;had looked
D was slipping ;looked
为什么选A

looked表被动,句子意思是当时没有人看他!而且when表明是当时正在发生的事,所以直接排除BCD,选A!