托福写作中虚拟语气怎么用？

虚拟语气(Subjunctive Mood)

用以表示不可能实现的愿望，想象，目的或者既不可能发生的事，或与事实相反的假设。这类句子通常由条件从句和主语从句构成。虚拟语气可分为三种：

1)与现实相反的假设

If I had enough money, I would/ could/ should travel around the world.

If I were you, I would/ might go with them aboard.

2)与未来事实相反的假设

If the program should fail, what should the government do?

If they should refuse the negotiation, we would prepare for the last hit.

注意：当条件从句should+动词原形，主句可用陈述句或祈使句

If it should rain tomorrow, we shall/ will not leave.

If it were to rain, we would call off the match.

If you went there next time, you would see what we experience.

(3) 与过去事实相反的假设

If I had study harder at school and home, I could/ might have passed this exam.

If they had had much money, they could have bought the sailboat.

4) 虚拟语气句子中时态的混合使用：有时主句表示与现在事实相反，条件从句表示与过去事实相反。

If they had started a few days earlier, they could finish before the deadline.

5) if 的省略：虚拟语气中的IF可以省略，但主语和助动词或be动词必须易位

Were Mary here now, she would explain the situation for you.

Should it happen, what would you do?

Had he recognized me, he would have come over.

(6) 虚拟语气在从句中的应用.

① 在表示愿望、请求、建议、命令等主观意愿的动词suggest, order, demand, propose, command, request, recommend, require, insist坚持要, desire, urge等动词的宾语从句以及would rather /sooner 后要用 “ (should) +动词原形” 来表示愿望,建议, 命令,要求等; 但是要注意的是当suggest表达“暗示”，insist表示“坚持某种说法”时，后面的从句不用虚拟语气，例如：Those clouds suggests that it is going to rain 或 The boy insisted that he did tell the truth to the police.

注意： 同样的在It is+上述动词的过去分词其后所跟的主语从句中也使用(should)+ 动词原形，如It is suggested that employees of this company wear uniforms on weekdays.

当然在上述动词相应的名词形式作主语+连系动词的形式中，其后的表语从句中，例如 The teacher’s suggestion was that class be re-scheduled.

这类名词suggestion, proposal, recommendation, demand, order, desire, request, requirement, insistence, advice, decision , obligatory, necessity义不容辞的, 必须的 等的同位语从句或表语从句中也要用相应的虚拟形式.

②) 在It is/was + 某些形容词 + that 从句的句型中,that从句中的谓语动词常用虚拟语气,即 “should + 动词原形”

这些形容词有: important, necessary, essential, imperative, natural, strange, advisable, desirable, possible, probable, astonishing, surprising, desired, suggested, requested, recommended, ordered, proposed, decided, moved等可表示惊奇,遗憾,怀疑,不满等.