----Have you finished your homework?
-----No, I my younger sister all day yesterday.
A. was looking after
B. would look after
C. had looked after
D. look after
网友回答
(答案→)A. was looking after
B. would look after
C. had looked after
D. look after
解析：考查时态。句意：你完成你的作业了吗？——不，我昨天整天都在照顾我的小妹妹。可知下文 描述的是过去一直在进行的动作，故用过去进行时态，故选A。