17.My sister _____ a letter when I got home last night.17.My sister ______ a letter when I got home last night.A.is writing B.was writing C.wrote D.is reading 我选的B 为什么

17.My sister _____ a letter when I got home last night.17.My sister ______ a letter when I got home last night.A.is writing B.was writing C.wrote D.is reading 我选的B 为什么
17.My sister _____ a letter when I got home last night.
17.My sister ______ a letter when I got home last night.A.is writing B.was writing C.wrote D.is reading 我选的B 为什么

17.My sister _____ a letter when I got home last night.17.My sister ______ a letter when I got home last night.A.is writing B.was writing C.wrote D.is reading 我选的B 为什么
选B. was writing ,这是明显的过去进行时的句子,表示过去某时正在做某事.这句话的意思是昨晚我到家的时候,我姐姐正在写信.

肯定 是答案错了 时间状语从句用的是一般过去时 主句也必须是过去时的一种 所以 你是对的