1.we"ll never forget the days _______ we spent together last year.a.when b.that c.how d.on which2.the high yellow building over there, _______ was set up last year, is our office building.a.it b.that c.where d.which3.it is the best tv play _______ i"ve seen.a.that b.which c.since d.and4.i often hear from my sister, _______ works as an engineer.a.that b.who c.he d.whom5.last month i visited the house _______ i used to live in my twenties.a.which b.who c.in that d.where6.the day _______ i was to start arrived at last.a.that b.which c.on which d.in that7.the old woman has two sons, _______ are teachers.a.two of whom b.both of whom c.all of them d.ne