原因状语从句because since as-2025-2026学年八年级英语下册语法考点精讲（教科版五四制）

八下外研版 【寒假专版】 B版考点精讲 寒假专版 原因状语从句：because,since,.as 语法专项突破 考点精讲 考点一：because,since,as引导原因状语从句的基本区别 规则：because语气最强，常回答why引导的问句，可位于句首或句末：since侧重于已知的、显 然的原因，意为“既然”，通常位于句首：s语气较弱，意为“由于”，引导的从句多位于句首。 例题1： （选择，外研七下期末真题改编)：一Why do you like English?一_it is interesting.A. Because B.Since C.AsD.So(答案：A) 例题2：（填空）：_you are free today,let's go to the park.(答案：Since) 例题3：Lit was late,we had to go home.(答案：As) 考点二：because与so不能连用 规则： because和so都是连词，在英语中不能同时出现在一个句子中，只能用其一。 例题1： (改错)：Because he is ill,so he can't go to school.(答案：去掉so) 例题2： 考点三：since/as引导的原因状语从句与主句的位置关系 规则：since//as引导的原因状语从句通常位于主句之前，有时也可位于主句之后，此时一般不用 逗号隔开。 例题l:(选择)：it is raining,we have to stay at home..A.Because B.Since C.SoD.But(答案： B) 例题2： (语法填空)：We didn't go out_it was too cold.（答案：as) 考点综合训练 一、 单项选择 1.-Why didn't Lucy come to the party?-she had to study for the exam. A.Because B.Since C.As D.So 八下外研版 【寒假专版】B版考点精讲 2.you finish your homework early,you can watch TV for an hour. A.Because B.Since C.So D.But 3.We had to walk homethere were no buses at that time. A.because B.since C.as D.so 4.it was raining heavily,we still went to the park. A.Because B.Since C.As D.Though 5.He didn't go swimming he was afraid of water. A.because B.since C.as D.so 6.you are free now,let's go shopping together. A.Because B.Since C.As D.So 7.-Why do you like pandas?-they are very cute. A.Because B.Since C.As D.So 8.the weather is fine,we will have a picnic tomorrow. A.Because B.Since C.As D.So 二、语法填空 1.We didn't go to the zoothe tickets were too expensive 2.you know the answer,please tell us quickly. 3.She was late for school she missed the early bus. 4.it was getting dark,we decided to stop working. 5.He can't play basketballhe hurt his leg yesterday. 6.you are here,let's start the meeting. 三、句型转换 1.He stayed at home because he was ill.(对划线部分提问) 2.Since it is cold,,you should wear a coat.(改为同义句) 3.Because she got up late,she missed the train.(改为同义句) 4.As there was no food left,we went out to eat.(改为同义句) 2 八下外研版 【寒假专版】 B版考点精讲 四、篇章填空 Last Sunday,Lily didn't go to the park with her friends.1.she had to help her mom with housework. 2.her mom was busy with work all week,Lily wanted to give her a break.In the morning,she cleaned her room 3.it was very messy.4.lunchtime came,she helped cook noodles.In the afternoon,her dad came back.5.he knew Lily had worked hard,he praised her.Lily felt happy 6.she could help her family 参考答案 一、单项选择 1.A2.B3.C4.A5.A6.B7.A8.B 二、语法填空 1.as 2.Since 3.because 4.As 5.because 6.Since 三、句型转换 1.Why did he stay at home? 2.As it is cold,you should wear a coat. 3.She got up late,so she missed the train. 4.Since there was no food left,we went out to eat. 四、篇章填空 1.Because 2.Since 3.as 4.As 5.Since 6.because 3