填：long before
这是long before 与before long 的用法区别问题.
1,before long “不久”的意思.单独使用.=soon,时间副词,可以用于一般将来时和一般过去时.如：I will be back before./ The settled in a new city.Before long they got married.
2,long before 是“老早”,“在.很久之前就已经.”,一般不单独使用.通常用于过去完成时.如：He had made the dinner long before his wife came home “他在妻子回家之前老早就做好晚饭了.”
3,It will (not) be long before +一般现在时.这是个固定句型,“XXX（不）会很久.”的意思.楼主的句子正是属于这种情况.
楼主句子的意思是：“过不了多久,他们就会互相理解的.”
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