(
课件网) 【知识精讲】原因状语从句 初三 英语 发布课文朗读任务 （任务-发布任务-自定义任务） 条件状语从句 时间状语从句 状语从句 原因状语从句 目的状语从句 结果状语从句 地点状语从句 比较状语从句 让步状语从句 方式状语从句 原因状语从句 定义 常用引导词 时态 原因状语从句的定义： 在句中用来说明主句原因的句子叫原因状语从句。 常用引导词: because (因为), as (由于), since (既然), for (因为) 时态：原因状语从句一般都是根据实际情况选用适当的时态。通常是主过从过，主现从现。 Because 引导的原因状语从句一般放于主句的后面，because从句位于句首时要用逗号分开，放在句末时，可不用逗号分开。 because表示直接原因， 语气最强， 最适合回答why引导的疑问句。because of 也表示原因，但它后面不接从句, 只能接名词, 代词或动名词。 注意：because 和so 不可同时出现在一个句子里。 引导词 because ① I do it because I like it. = I like it so I do it. ② We went by bus because it was cheaper. = It was cheaper so we went by bus. ③ Because he was tired, he couldn’t walk here. =He was tired, so he couldn’t walk here. 引导词 because since “既然”表示对方已知或客观的事实或理由，常放在句首，较为正式， 语气比because弱。 ① Since you’re interested in English, why not have a try in the English Speech Contest ② Since you are free today, you had better help me with my mathematics. ③ Since you don’t trust him, you should not employ him. 引导词 since as 引导原因状语从句时表示附带说明的“双方已知的原因”，含有对比说明的意味，语气比since弱，较为正式，位置较为灵活(常放于主句之前)。 ① As he is ill, he can’t come to the meeting. ② As you weren’t there, I left a message. ③ As you are tired, you had better rest. 引导词 as for 引导的是并列句表示原因但并不说明主句行为发生的直接原因，只提供一些辅助性的补充说明。for引导的并列句只能放于主句之后并且必须用逗号将其与主句隔开。 ① It must have rained last night, for the ground is wet. ② He could not have seen me, for I was not there. ③ He seldom goes out now, for he is very old. 引导词 for Why didn’t you come -- _____my father would not let me. Why didn’t you come -- _____my father would not let me. 答案：Because 单项选择。 _____ you know little about the Song Dynasty, you'd better find a book to learn more. A. Unless B. While C. Though D. Since 单项选择。 _____ you know little about the Song Dynasty, you'd better find a book to learn more. A. Unless B. While C. Though D. Since 答案：D
