第1个回答 2014-12-20
1. (表示条件)如果 ,主句用将来时，if从句用现在时表示将来
He will come if you invite him.
如果你请他,他会来的。
2. (表示虚拟)假如,要是
1）时态：可以表示过去，现在和将来的情况。它的基本特点是时态退后。
a. 同现在事实相反的假设。
句型 ： 条件从句 主句
一般过去时 should( would) +动词原形
If they were here, they would help you.
b. 表示于过去事实相反的假设。
句型： 条件从句 主句
过去完成时 should(would) have+ 过去分词
If she had worked harder, she would have succeeded.
The rice would not have been burnt if you had been more careful.
If my lawyer had been here last Saturday, he would have prevented me from going.
If he had come yesterday, I should / would have told him about it.
含义：He did not come yesterday, so I did not tell him about it.
If he had not been ill and missed many classes, he would have made greater progress.
含义： He was ill and missed many lessons, so he did not make greater progress.
c. 表示对将来的假想
句型： 条件从句 主句
一般过去时 should+ 动词原形
were+ 不定式 would + 动词原形
should+ 动词原形
If you succeeded, everything would be all right.
If you should succeed, everything would be all right.
If you were to succeed, everything would be all right.
3. 是否 = whether 连接宾语从句
I wonder if she is ill.
不知她是否病了。追答
He will come if you invite him.
如果你请他,他会来的。
2. (表示虚拟)假如,要是
1）时态：可以表示过去，现在和将来的情况。它的基本特点是时态退后。
a. 同现在事实相反的假设。
句型 ： 条件从句 主句
一般过去时 should( would) +动词原形
If they were here, they would help you.
b. 表示于过去事实相反的假设。
句型： 条件从句 主句
过去完成时 should(would) have+ 过去分词
If she had worked harder, she would have succeeded.
The rice would not have been burnt if you had been more careful.
If my lawyer had been here last Saturday, he would have prevented me from going.
If he had come yesterday, I should / would have told him about it.
含义：He did not come yesterday, so I did not tell him about it.
If he had not been ill and missed many classes, he would have made greater progress.
含义： He was ill and missed many lessons, so he did not make greater progress.
c. 表示对将来的假想
句型： 条件从句 主句
一般过去时 should+ 动词原形
were+ 不定式 would + 动词原形
should+ 动词原形
If you succeeded, everything would be all right.
If you should succeed, everything would be all right.
If you were to succeed, everything would be all right.
3. 是否 = whether 连接宾语从句
I wonder if she is ill.
不知她是否病了。追答
我在百度上搜的，用解释么？
总结就是 ①是否：引导宾语从句，要根据具体情况来使用时态，常用一般将来时
②如果：引导条件状语从句，用法是“主将从现”，即：主句用将来时态，if从句用一般现在时态
第2个回答 2014-12-20
是否 如果追问
都怎么用
追答按意思用
否则if的语法很多 ，你也才初二啊
追问那就这个题里的用法呢
追答上一个是是否的意思，后一个是如果的意思
追问上一个后面接的必须是将来时么
追答这里考的是关于将来时的用法，与if关系不大
追问啊，谢谢
本回答被提问者采纳第3个回答 2014-12-20
A追答
第一个if 是 是否的意思，第二个是 主将从现，主句用将来时态，从句用一般现在时
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