經(jīng)典例句]
1.If you copy my homework this time,you will start a bad habit.
2.I’ll ask the teacher for help if I don’t understand.
3.If the traffic lights are red,you must stop and wait.
4.You can pass the exam if you work hard
= Work hard,and you will pass the exam.
5.If you don’t hurry up,you will be late again.
= Hurry up,or you will be late again.
[要點演繹]
◆結(jié)構(gòu)：if是從屬連詞,意為“如果”,用來引導(dǎo)條件狀語從句.if引導(dǎo)的條件狀語從句既可放在主句之前,也可放在主句之后.從句位于主句之前時,常用逗號將其與主句隔開.如句1、3、5.
◆時態(tài)：主句用一般將來時 （如句1、2）或主句謂語中含情態(tài)動詞 （如must,can,could,should等,如句3、4） 時,if引導(dǎo)的條件狀語從句用一般現(xiàn)在時表示將來意義.
◆變換：含有if引導(dǎo)的條件狀語從句的復(fù)合句中,當(dāng)主句主語和從句主語均為you時,可轉(zhuǎn)換為“祈使句,and + 簡單句 （如句4）”或“祈使句,or + 簡單句 （如句5）”.