If I should ……, I will ……

　　结构�UIf…should…，…would（will）/should（shall）等+原形动词

　　说明�U这是表示与未来事实相反的假设<句型>，if <子句>要用<助动词> should，译成“万一”。should可置于<主词>前，将 if 省略。<主要子句>的<助动词>则视可能性做变化：若可能性低，则为过去式，若可能性高，则为现在式。should 可以提前，而将 if 省略。

　　If he should come, I would tell him the truth.
　　万一他来，我会把真相告诉他。

　　If he should come, I will tell him the truth.
　　万一他来，我一定会把真相告诉他。

　　Should the boy come again, I would throw him out.
　　要是那男孩在来，我就把他撵出去。

　　If it should rain, our plan would be spoiled.
　　万一下雨，我们的计划就泡汤了。

　　Should that be true, the contract would be canceled.
　　假如那是真的，合约就该取消。

　　Should another world war break out, what would become of human beings?
　　万一另一次世界大战爆发，人类将会发生什么事?