【问】 “在表示将来情况的条件从句中，有时可用‘were to(should)+动词原形’来构成谓语：

If I were to(should) do it，I would do it in a different way.要是我来做这事，我会是另一种做法。

If they were to(should) act like that again，we should criticize them severely.要是他们再这样做，我们就要严厉地批评他们。

We wouldn't lose courage even if we should (were to) fail again.即使再次失败我们也不会泄气。

If they should attack us，we would wipe them out completely.如果他们胆敢袭击我们，我们就彻底消灭他们”。(张道真编著《实用英语语法》，1995年，P.211)

根据以上的论述，if... were to+动词原形和if... should +动词原形是可以互换的。我的问题是：难道它们之间就一点区别也没有吗?

【答】 if... were to+动词原形与if... should+动词原形有一些细微的差别。第一，if... wereto+动词原形主要用于正式语体，因此在科技英语里极为常见;第二，if... were to+动词原形表示将来发生某事的可能性极小，有时候，在说话人看来，是根本不可能发生的。

1. What would you do if war were to break out? (PEU)

万一发生战争，你怎么办? (在说话人看来，战争是不会发生的)

2. If he were to do this work，he might do it in another way.

倘若他来做这项工作，他可能用另一种方法来做。(说话人认为事实上他不可能来做这项工作)

3. If we were to travel by space rocket to the moon we would find it quite a different placefrom our own planet—the earth.

如果我们乘宇宙火箭到月球上去旅行，我们将会发现，月球与我们自己的星球——地球是完全不一样的。