() it rain tomorrow，we would have to put off the vist to the Yangpu Bridge {A, Were B,Should}

本句是虚拟语气,条件句省略了IF,做了倒装,
虚拟语气表示将来完成的情况,条件句只能用SHOULD,从句用WOULD +现在完成时

If it should be rain tomorrow，we would have to put off the vist to the Yangpu Bridge。
当省略if时，be也要省略，句型为 助动词+主语+动词短语，从句
应该是这样的吧，我觉得用would好像更好。有这个选项吗