一、含蓄条件句
有时假设的情况并不以条件从句表示出来,二是暗含在上下文中,比如通过介词短语来表示。这些介词常是：but for, without, otherwis等。如：
but for your advice, i could not have done it so successfully.
如果不是听了你的建议，我就不会做的如此成功。
the change could not have taken place without the open-door policy.
没有开放的政策，就不会有如此大的变化。
i was so busy then, otherwise, i would have told him the answer.
我当时很忙，否则，我就会把答案告诉他的。
二、虚拟语气在某些从句中的应用
1、wish后的宾语从句(would rather (sooner) 后也是如此)
i would rather they came tomorrow. 我宁愿他们明天来。
how i wish it wasn’t raining now. 如果现在不下雨该多好呀!
i wish i had not been to yesterday’s party. 我要不去参加昨天的宴会就好了!
但would rather 后没有主语则应使用零不定式.
2、suggest, order, demand, propose, command, request, desire, insist 等动词后的宾语从句
they demanded that the aggressor troops (should) be withdrawn immediately.
他们要求侵略者立刻撤退。
i propose that we (should) set a deadline for handing in the plan.
我提议应该制定一个交计划的最后期限。
3、it is desired, it’s suggested, it’s requested, it was ordered that, it was proposed that, it is necessary that, it is important that, it has been decided that 等之后的主语从句：
it is necessary that he (should) be sent there at once. 有必要立刻派他前往。
it’s required that mr. lee (should) give a performance at the party.
要求李先生在晚会上出个节目。
it’s desired that we (should) get everything ready by tonight.
要求我们在今晚前把一切准备好。