最新if引导虚拟条件句.doc

Four short words sum up what has lifted most successful individuals above the crowd: a little bit more.-author-dateif引导虚拟条件句if引导虚拟条件句if既可以引导宾语从句又可以引导状语从句。if充当宾语从句的连接词时，相当于whether，词义为“是否”，遵循宾语从句的时态规则；充当从属连词，引导条件状语从句时，词义为“如果”，若主句中的谓语动词用一般将来时，则从句中的谓语动词通常用一般现在时表示将来。例如：1 I will go out tomorrow if it is fine.2 I don't know if the train has arrived.句1中if引导的是状语从句。这个从句表示“条件”，修饰主句。整个句子的意思是“如果明天天气好，我们就出去。”句2中if引导的是宾语从句，充当谓语动词don't know的宾语。整个句子的意思是“我不知道火车是否到了。”虚拟语气在条件状语从句中的用法 1. 表示与现在事实相反的情况，其句型为“ if+ 主语 + 动词的过去式（ be 动词用 were ），主语 +would / could / might / should + 动词原形”。如： If the weather were fine, we would go to Shanghai. 如果天气好，我们就去上海。（事实上天气不好） If they had time, they would / could / might go with me. 如果他们有时间，他们就会（可能）和我一起去。 2. 表示与过去事实相反的情况。其句型为“ if + 主语 + 动词的过去完成式，主语 +would / could / should / might + have + 动词的过去分词”。如： If I had taken his advice, I shouldn't / wouldn't / couldn't have made such a mistake. 如果我按照他的建议去做，我一定不会（不可能）犯这样的错误。 3. 表示与将来事实可能相反的假设和结果，其句型为“ if + 主语 + 动词的过去式 / should + 动词原形 / were to + 动词原形，主语 +would / could / might / should + 动词原形”。如： The glass would break if you dropped it. 杯子摔下来会打破的。（事实上没有摔下来） If it should rain, the crops would / could / might be saved. 假如天下雨，庄稼就一定（有可能）会得救。 注意：主句中的 should 只用于第一人称，但在美国英语中， should 常被 would 代替；从句中的 should 可用于各种人称。-