新概念英语词汇随身听速记手册1-新概念英语词汇随身听手册一if从句

一、if引导状语从句，表示”如果...”，”假使...”。
if引导状语从句是对就现在,过去,未来可能实现之事加以推测。
例如：If I win a lot of money I'll buy you a mink coat.如果我赢了钱，我会给你买件貂皮大衣(新概念一册第137课)。
If you park your car in the wrong place, a traffic policeman will soon find it.
如果你把车停在不应该停的地方，交警会找到你的(新概念第二册第16课)。
二、if用于虚拟语气中
1.与现在事实相反:
从句动词过去式，主句用would/could/should/might+动词原形。
例如：If I were you, I would ask him his telephone number.如果我是你，我会问他的电话号码的。
If I were you, I would help him 如果我是你,我会帮助他。
2.与过去事实相反：
从句had+动词过去分词，主句would/could/should/might+have+动词过去分词。
例如：If I had known, I wouldn't have done it. 假使我知道,我就不会做那件事。
If you ate more and talked less, we would both enjoy our dinner! 如果你少说多吃，我们都会很享受那顿晚餐的!(新概念英语第二册第40课)
3. 与将来事实相反：
从句should/were to + 动词原形，主句would/could/should/might+动词原形
例如：If it should rain, the crops might be saved. 如果下雨，庄稼就有救了。
If it should rain tomorrow, I shall not [shan't, won't] come 万一明天下雨,我就不来。
三、if引导宾语从句，表示“是不是...”基本等同于whether
例如：Ask him if it is true 问他那是不是真的
I wonder if he is in the school 我不知道他是否在学校

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