英语：It was 2000 when I graduated from university.这句话when 引导的是时间状语从句,It代什么?不是主语从句吧.请把这个简单的句子分析下

英语-Unit 9 When was it When was it taken When was it built? when was it 英语 Can you tell me__________?A.when did it happen B.when it happened C.when was it happened D.when it was happened为什么不是D 求关于when was it invented的英语作文 when it was so warm It was in 2000 when he was in middle school 这个句子为什么不用强调句It was.that结构? Billy started painting when he was four years old.When he was six,he was already very good at it .H有关如题的英语文章 英语 it was... 英语：九年级第九单元When was it invented?这一单元的重点语法和内容 英语改错问题It was on October 1st 1949 when the People's Republic of China was founded. When was it的中文意思是什么 I Was There When It Happened 歌词 He was sleeping late when it arrived 求when it was me 中文歌词 It was s_ when I woke up. when was it invented?是人教版九册第几单元?