1.Before Mary came here,she_had_studied___(study) inAustralia.
2.As nothing could__be done_____(do)at that moment.
3.It was the thirld time that the girl__had invented_____(invent)him to her party.请解释一下第2、3题第二题是被动语态，事情被做第三题it was time that sb. had done句型