It was over two years since I came back from the countryside.改错.这句为什么不可以

题目

It was over two years since I came back from the countryside.改错.这句为什么不可以
那改成It is over two years since I came back from the countryside.
这类it开头的句子是何方神圣?我最搞不懂了.有什么方法解决呢

答案

可以,答案就是 It is over two years since I came back from the countryside.
这里一个固定句型：It is / has +一段时间+ SINCE 从句（ 从句要用过去时）
加油!不明白再问!