if引导的真实条件句
If you want to watch this film, I will buy two tickets.
If I buy two tickets, we can go to the cinema.
If we are watching the film, please keep quite.
从句谓语中有 be
方法一：
主从句主语相同,if从句中有 be,则if从句中主语、
谓语可省略。
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Have a try
1.If you are studying English , you must pay attention.
2.If two rivals meet , the strongminded one will win.
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Have a try
1.除非你确立了目标 ，否则你就会失去方向。 Unless you set goals, you will lose your
way. 2. 如果你不快点，你就见不到Eason。 Unless you hurry up, you won’t see Eason.
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主谓语省略
If you have finished dinner, I’ll ask the waiter for the bill.
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主将从现
主句将来时 从句现在时
一般将来时 祈使句 含情态动词 一般现在时 现在进行时 现在完成时
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• 如果你拉猫的尾巴，它就会抓(scratch)你。 If you pull the cat’s tail, it will scratch you. • 如果你想减肥，你应该少吃糖。 If you want to lose weight, you must eat
do something. 3.如果明天天气好，我们就去划船。 If ( it is) fine tomorrow , we will go boating.
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4.如果有必要，你要再试一次。 If (it is) necessary, you will try again.
5.如果是真的，这条信息会很重要。 This information will be important, if (it
is) true.
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unless引导真实条件句
• We can’t watch the film unless we buy tickets. We can’t watch the film if we don’t buy tickets.
• We will miss the film unless we hurry up. We will miss the film if we don’t hurry up.
If Eason is not invited, he won’t come to the party.
Unless Eason is invited, he won’t come to the party.
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unless= if not (除非…否则，如果不)
1. 如果你30岁还没结婚，你就成了一个剩女。 Unless you get married in your 30, you will be a 3S lady.
2.如果你不积极寻找白马王子，你就会错失良机。 Unless you hunt for your Mr.Right actively, you will miss the opportunity.
3.If he is free , he will go with us. 4.If you want to have happiness , you
will get health , knowledge and virtue.
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1.如果冰被加热，它就会变成水。 If heated, the ice will turn to water.
If you are offered help, you must never forget to say Thank you.
If offered help, you must never forget to say Thank you.

If (you are) in Rome , you must do as Romans do. 主句，从句主语相同
If (it is) necessary, he will turn to police for help.
If it is possible, he will call the police. If (it is) possible, he will call the police.
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If (it is) necessary , I’ll explain to you again.
less candy.
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Lecture Twelve
Grammar
if 引导真实条件句中
主谓语省略
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If he is in trouble, he will turn to police for help.
If in trouble, he will turn to police for help.
2.如果你在武汉，你可以尝尝热干面。 If in Wuhan, you can try hot-dry noodles .
3.如果你正在开车，你应该专心。 If driving, you must drive with concentration.
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If it is necessary, he will turn to police for help.
方法二： if从句中主语是it ,谓语中有 be,则if从句中主语、谓 语可省略(it be 省略)。
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Have a try
1.回答这些问题，如果可能的话不要参考书本。 Answer these questions ,if ( it is ) possible without referring to the books. 2.如果有必要，你可以帮我们做点事。 If ( it is ) necessary , you can help us to