第1个回答 2020-07-10
答案：My sister was playing the piano when I got home yesterday．这是一个陈述句，是一个主从复合句，用when引导的时间状语从句，从句是说昨天当我到家时，说的昨天yesterday的事，用一般过去时，主语I，到达用get to，这里是到家，home是副词，故介词to省略，故 when I got home yesterday．主句是说的是妹妹正在弹钢琴，说正在做某事，用过去进行时was/were+doing，主语是my sister，故was，弹钢琴play the piano，故My sister was playing the piano，故答案是My sister was playing the piano when I got home yesterday．