_______today ,he would get there by friday为什么选 were he to leave 哪里看出是倒装?为什么用were

这是省略if的倒装
在if引导的虚拟语气中，谓语动词有were、had或should等时,可以将if省掉,把这些词语移到主语之前。如：
Were I you（=If I were you）, I would do thework better.
Had they time (=If they had time) ，they should certainly come and help us.
Should there be a flood (=If there should be a flood), what should we do?
上面的句子相当于
If he were to leave today, he would get there by Friday.
注意，在虚拟语气的从句中，动词be的过去时态一律用were，不用was。

（1）were he to leave 正常语序是：he were to leave ，此句子将were提到句首，故这个句子是倒装。 be to 表将来。
（2）用were 因为是虚拟语气，与现在事实相反的虚拟语气；条件从句用一般过去式，而主句用“主语+would（should）+谓语动词”结构。

原句是,if he were to leave today,整句话的意思是,如果今天离开的话,他星期五就能到达那里.（但实际他今天没有离开,这里用虚拟句）be to do sth 表安排好的事,或将要发生的动作,用were是表示虚拟.这种句子倒装,就是...