“It be some time+ since短语或从句” 这里面的be用哪种形式呢?is,was还是has been呢

“It be some time+ since短语或从句” 这里面的be用哪种形式呢?is,was还是has been呢 It is/has been +时段+since从句 It was/be+时段+before从句 用些这英语句型造个句 什么时候用It be some time+since从句,什么时候用It be some time +that 从句 it is some time since+...与it has been some time since+...什么区 为啥it is some time since与it has been some time since没区别 it has been some time+since是什么意思 为啥it is some time since与it has been some time since没区别谢谢了, It is/has been…since… It was/will be…before… 这两个句 it is 时间段since从句和it has been时间since从句的区别 it is four years since I joined the army.这里的is,为什么不用was呢? It __four years since i joined the army.这里的is,为什么不用was呢? It's a long time since还是It has been a long time since