1,Mr Black had taught in this school by 1970（改为否定句）Mr Black _ _ _ in this school by 19702,By the end of last term, we _ (learn) about three thousand English words.3,He had cleaned the room by eight o'clock yesterday.( 改为一般疑问句）3,_ he _ the room by eight o'clock yesterday?4,John had seen the film before, _ _ (完成反意疑问句）希望各位英语高手能指点一下过去完成时的一般疑问句,反意疑问句等怎么写?

1,Mr Black had taught in this school by 1970（改为否定句）
Mr Black had not taught in this school by 1970
2,By the end of last term,we had learnt (learn) about three thousand English words.
3,He had cleaned the room by eight o'clock yesterday.( 改为一般疑问句）
3,Had he cleaned the room by eight o'clock yesterday?
4,John had seen the film before,hadn't he (完成反意疑问句）
否定句:had not动词过去分词
一般疑问句:had提前