it was the first time 后面为什么要用过去完成时

it was the first time 后面为什么要用过去完成时 the first time i saw it was three year ago要过去式还是过去完成时为什么? it was the first time连接过去时还是过去完成时? 用 it is/was the first time that＋过去完成时造句 That was the first time (that) I had been in Rome.为什么用过去完成时? It was for the first time that后面从句用什么时态 it is the first time和it was the first time后面接的时态各是什么? 为什么“this is the first time i have baked it"为什么后面用现在完成时? it is the first time that I -have come to BeiJin为什么要用完成时啊,后面 it was the first time that he experienced.为什么用THAT 不用WHEN ,是 It was the first time that I ----- ------ ----- ----- ------ 用for.the.first.time和at.first 和it.was.the.first.time和the.firs