如题所述
第1个回答 2012-04-20
1、对现在情况的假设：表示说话时不存在或与事实相反的情况。形式：If+主语+did，主语+should/ would /could +do.例句：If you knew english well,you would be able to talk with foreigners freely.
2、对过去情况的假设：表示与过去事实相反的情况。形式：if+主语+had done,主语+should/would /could+have done.例句：if i had not studied hard ,i might have failed in the exam.（事实是我通过考试了）
3、对将来情况的假设：表示将来实现可能性不大的情况。形式：if+主语+did/were to do /should do,主语+should /would /could do.例句:if he should change his mind ,what would we do?
if的省略：在正式文体中，有时可把虚拟条件句中的连词if省去，这时从句需要采用倒装语序，即：将were,had,should等助动词提到主语前面，主句不做任何变化。例句：should it rain tomorrow,we would staly at home.
错综时间：所谓错综时间是指主句和从句的动作不是发生在同一时间。这时，需要根据意思选用表示不同时间的虚拟语气形式。例句：if i were you ,i would have taken his advice.（从句表示现在时间，主句表示过去时间），我要是你，就听他的忠告了。
2、对过去情况的假设：表示与过去事实相反的情况。形式：if+主语+had done,主语+should/would /could+have done.例句：if i had not studied hard ,i might have failed in the exam.（事实是我通过考试了）
3、对将来情况的假设：表示将来实现可能性不大的情况。形式：if+主语+did/were to do /should do,主语+should /would /could do.例句:if he should change his mind ,what would we do?
if的省略：在正式文体中，有时可把虚拟条件句中的连词if省去，这时从句需要采用倒装语序，即：将were,had,should等助动词提到主语前面，主句不做任何变化。例句：should it rain tomorrow,we would staly at home.
错综时间：所谓错综时间是指主句和从句的动作不是发生在同一时间。这时，需要根据意思选用表示不同时间的虚拟语气形式。例句：if i were you ,i would have taken his advice.（从句表示现在时间，主句表示过去时间），我要是你，就听他的忠告了。
