过去完成时 had done
时间标志
by last year/by the time of
过去完成时一般和过去时一起出现
sb had done sth before sb did
sb did sth after sb had done
用于hardly when,no sooner than的句式中
we had hardly came home when it rained.
用在“It was the first/second...time+that”句型中