过去进行时过去进行时：Iwaswalkingdownthestreetwhen it began to rain.WhenitbegantorainIwaswalkingnowIwaswalkingdownthestreetwhenitbegantorain.Iwasnotwalkingdownthestreetwhenitbegantorain.Wereyouwalkingdownthestreetwhenitbegantorain? 1关键词：was/weredoing 2、句子结构： 肯定句：主语+was/were+现在分词+其他 否定句：主语+wasnot/werenot+现在分词+其他 疑问句：was/were+主语+现在分词+其他 肯定句：主语+was/were+(doing)+其他. Iwasplayingbasketballat6:30yesterday. Hewasplayingthepianoatthatmoment. Theyweredoinghomeworkat8:00lastnight(2)否定句：主语+was/were+not+（doing）+其他 Iwas
