过去进行时的基本概念
过去进行时(past continuous tense)表示过去某一时刻或某段时间正在进行的动作。如: I was practicing the violin at eight o'clock yesterday evening. 昨晚八点钟我正在练习小提琴。 When Walter arrived home,his sister was doing her homework.沃尔特到家时,他妹妹正在做作业。 Pat was watching TV all evening. 帕特整个晚上都...