what would you do if you saw the traffic accident ,不是主将从现么

虚拟语气分为：与现在事实相反,与过去事实相反,与将来事实相反
第一种：与现在事实相反,从句用过去时,did或were,主句用would+动词原形
例句:If I were you,I would not study English.
第二种：与过去事实相反,从句用had done,主句是would/could/should have done
例句：If you had come yesterday,you would/should/could have seen her
第三种：与将来事实相反,从句分三种
1、与现在事实相反用法一样
2、were to do
3、should do这里should不可替换,主句用could/would +动词原形
例句
1.If you came tomorrow,you would see me
2.If you were to come tomorrow,you could/would see me
3.If you should come tomorrow ,you could/would see me