这道题考察的是虚拟语气中条件从句的倒装,这道题是对未来情况的假定,适用的语法规则为：
句型：条件从句 主句
一般过去时 should+ 动词原形
were+ 不定式 would + 动词原形
should+ 动词原形
楼主说的对,倒装有 were had 和 should ,但其实were to 也是可以的,因为可以把 were to 看成是 were 的将来时用法.所以选C Were he to leave
原来的语序是if he were to leave today,he would get there by Friday.
倒装后：Were he to leave today,he would get there by Friday.
希望能帮到楼主,要是答案还满意的话,记得采纳哦,!如果有任何疑问,