If 的两种用法

“ 【1 】if”的两种用法|：
一．意为“是否”时,引诱宾语从句.应遵守的时态是：
①主现从随意率性.即：当主句为一般如今时的时刻,从句可依
据本身的时光短语断定该用什么事态,不受主句的影响.
②主过从过.即:
当主句为一般曩昔时的时刻,从句应用曩昔的某种时态.
③[留意：①宾语从句要用陈述语序,即：主语在前,谓语动词在
后]
Eg: He asks if I Like English. （主现从随意率性）
He asks if I am going to the party this evening. (主现从随意率性) He aske d if I liked English. (主过从过)
He aske d if I was going to the party this evening.(主过从过) 二．意为“假如”时,引诱前提状语从句.应遵守的事态是：①
主将从现.即：当主句为一般未来时的时刻,从句应用一般如今
时.
②主现从现.即：当主句为一般如今时的时刻,从句应用一般如今时.
③主过从过.即：当主句为一般曩昔时的时刻,从句应用曩昔的某种
时态
Eg: If you go the party, you will have a great tim e！ (主将从现)
If you ride your bike to school, you’ll be late.(主将从现)
If you don’t have your ID card,you can’t go to the party.(主现从现)
If you don’t listen carefully in class,you can’t do your homework. (主现从现)
If you got up earlier this morning, you wouldn’t be late.(主过从过)
If you didn’t finish your homework,the teacher would be angry with you.(主过从过)
“if”时,要先断定“if”
是哪种意思,再断定时态.
Eg:Mary asks me if I will go to the zoo with her next Sunday;
If it doesn’t rain, I will go with her.
剖析:第一个“if”意为“是否”,所以它引诱的是宾语从句;又因主句是一般如今时,从句里的时光短语为next Sunday,所以从句该应用一般未来时.即：主现从随意率性.
第二个“if”意为“假如”,所以它引诱的是前提状语从句;又依据高低句接洽,断定时光词也是next Sunday,所以主句该用一般未来时,从句该用一般如今时.即：主将从现.
2.If引诱的前提状语从句可与“祈使句+and/or+句子（一般未来
时）”这一句型互相转换.个中and暗示顺承,意为“那么”;or 暗示转折,意为“不然”.如：
If you work hard,you will pass the exam easily.
= Work hard,and you will pass the exam easily.
=Work hard,or you won’t pass the exam easily.。