原因与条件状语从句-2025-2026学年八年级英语下册语法重难点精讲（译林版）

8下译林版 【寒假专版】 原因与条件状语从句精讲 寒假专版 【语法专题】原因与条件状语从句专项突破 初中译林版八年级下册 语法精讲 语法概述：原因状语从句(because,since,as,for)=说明主句动作发生原因的句子，在句中作原因 状语；条件状语从句(if,unless,as long as)=说明主句动作发生条件的句子，在句中作条件状语。 重难点讲解 重难点一：原因状语从句的引导词辨析讲解： because表示直接原因，语气最强，常用于回答why引导的疑问句，不能与so连用。 Ie stayed at home because he was ill.(直接原因) Why were you late?Because the bus broke down.why) since/as表示已知的、显然的原因，语气较弱，常译为“既然/由于”，since稍正式，as更口语化。 Since everyone is here,let's start the meeting.(已知事实) As it was raining,we decided to stay indoors.(显而易见的原因) 真题再现： 1.(2024江苏南京期中，译林版)一Why didn't Lucy go to the party yesterday?-一_she hadto look after her sick mother A.Because B.Since C.As D.For 答案：A解析：问句用why提问，答句需用because说明直接原因。 2.(2023江苏苏州月考，译林版)_you know the answer,.please raise your hand. A.Because B.Since C.So D.Though 答案：B解析：“知道答案”是已知事实，用since引导原因状语从句，表“既然”。 1 8下译林版 【寒假专版】 原因与条件状语从句精讲 重难点二：条件状语从句的时态规则讲解： if/unless引导的条件状语从句中，主句用一般将来时，从句用一般现在时（主将从现）：主句含情 态动词(can/may/must等)或为祈使句时，从句也用一般现在时。 If it rains tomorrow,we will stay at home..(主将从现) You can pass the exam if you study hard.(主句含情态动词) Don't go out unless your parents agree.(祈使句，unless=-if...not) 真题再现： 1.(2024江苏无锡期末，译林版)If he free tomorrow,he to the park with us. A.will be;goes B.is;will go C.is;goes D.will be;will go 答案：B解析：f引导条件状语从句，遵循“主将从现”，从句用一般现在时s,主句用一 般将来时will go。 2.(2023江苏常州期中，译林版)You get good grades unless you_hard, A.won't;study B.will;study C.don't;study D.will;don't study 答案：A解析：unless表“除非”，从句用一般现在时study,主句用一般将来时，结合语境 需用否定won't。 重难点三：unless与if.not的转换及用法讲解： unless意为“除非：如果不”，可与f.not互换，但unless引导的从句只能用于真实条件句，不可 用于虚拟语气：当从句是否定句时，只能用if.not,不能用unless。 You will fail unless you work hard.You will fail if you don't work hard.( Iwon't help you if you don't ask me.(从句否定，不可用unless) 真题再现： 1.(2024江苏扬州月考，译林版)We will have a picnic this Sunday unless it一 A.rains B.will rain C.rained D.is raining 答案：A解析：unless引导条件状语从句，“主将从现”，从句用一般现在时rains,unless=-if.not。 2.(2023江苏镇江期中，译林版)You can't watch TV_you finish your homework first. A.unless 2 8下译林版 【寒假专版】 原因与条件状语从句精讲 B.if C.because D.when 答案：A 解析：句意为“除非先完成作业，否则不能看电视”，unless符合语境，=if you don't finish。 重难点四：状语从句的位置及逗号使用讲解： 原因/条件状语从句可位于主句前或主句后。从句位于主句前时，需用逗号与主句隔开：位于主句 后时，不用逗号。 Because he was tired,he went to bed early..(从句在前，用逗号) He went to bed early because he was tired.(从句在后，无逗号) If it snows,.we will make a snowman.（从句在前，用逗号) We will make a snowman if it snows.(从句在后，无逗号) 真题再现： 1.(2024江苏南通期末，译林版)_the weather is fine tomorrow we will go hiking.. A.Because B.If C.So D.Though 答案：B解析：从句“天气好”是主句“去远足”的条件，且从句位于主句前，需补充引导 词f。 2.(2023江苏泰州期中，译林版)She didn't go to school yesterday_she was ill A.So B.because C.but D.and 答案：B解析：从句“生病”是主句“没上学”的原因，位于主句后，用because引导，无 逗号。 易错点综合演练 I单项选择（直击重难点） 1.-Why did Mark refuse the invitation? he needed to prepare for the exam. A.Because B.Since 3 8下译林版 【寒假专版】 原因与条件状语从句精讲 C.As D.For 2.you have finished your homework,you can watch TV for half an hour. A.Because B.Since C.Unless D.Though 3.If it sunny tomorrow,we a picnic in the park. A.will be;have B.is;will have C.is,have D.will be;will have 4.You catch the early bus unless youup now A.don't;get B.won't;get C.won't;will get D.don't;will get Ⅱ用所给词的适当形式填空（强化句型结构） 1.He didn't go to school yesterday because he (be)ill 2.(since)everyone agrees,we will start the project next week. 3.If she(study)hard,she(pass)the exam easily. 4.You (not succeed)unless you(try)your best. Ⅱ.短文填空（综合运用状语从句） 用because,.since,.if,unless的适当形式填空，使短文完整通顺。 Tom was late for school this morning.1.he missed the early bus.His teacher asked,"2.you usually get up early,why were you late today?"Tom said,"I overslept.But I promise,3.I go to bed early tonight,I 4.be on time tomorrow."The teacher smiled and said,"You won't improve 5. you change your bad habits. V.按要求改写句子（巩固语法规则）》 1.He stayed at home because he had a cold.(对划线部分提间) he at home? 2.If it rains tomorrow,.we will cancel the trip.(改为同义句) We will cancel the trip it rain tomorrow. 4 8下译林版 【寒假专版】 原因与条件状语从句精讲 3.Since you know the truth,.please tell us..(改为一般疑间句) tell usyou know the truth? 4.You will fail the exam unless you study hard.(改为同义句) You will fail the exam you study hard. 综合演练参考答案 I.单项选择：1.A2.B3.B4.B Ⅱ.用所给词的适当形式填空：1.was2.Since3.studies,will pass4.won't succeed,ty Ⅲ短文填空： 1.Because 2.Since 3.if 4.will 5.unless V.按要求改写句子： 1.Why did;stay 2.unless;doesn't 3.Will you;since 4.if,don't 5