1.These old pictures bring to their mind the college days___

1.These old pictures bring to their mind the college days____they spent together,______life was hard but happy.A.which;when B.when;which C.which;which D.when ;when2.-Why was Professor Johnson unhappy those days?-Can't you see it clearly The only reason was that the theory he insested on
___wrong.A.proving B.being proved C.proved D.was proved3.-Has Young Joy returned from Yunnan yet I'd like to meet her.-I'm terribly sorry ,but she ____back here only for last weekend.A.has been B.would be C.was D.had been都选什么?为什么?