人教版八年级下册Unit 8 Making a Difference 单元语法知识梳理与练习（原卷版+解析版）

人教版八年级下册Unit 8单元语法知识梳理与练习 一：单元语法知识梳理 (Unit 8 Making a Difference) 一、现在完成时与 for / since 的连用 (Present Perfect with for and since) 【规则变化】 现在完成时可以表示某一动作或状态从过去某一时间开始，并一直持续到现在。此时，通常需要和表示延续的时间状语（如 for 或 since 引导的短语/从句）连用。 提问这种持续了多久的动作或状态时，需要使用 How long... (多久……？)。 【注意】 用于表示持续动作或状态的动词，必须是延续性动词（如 live, teach, study, work, keep, be 等）。 【例句】 —How long have you been a volunteer 你做志愿者多久了？ —I have been a volunteer here for a few months. 我在这里做志愿者好几个月了。 She has taught English to the soldiers for three years. 她教士兵英语已经三年了。 二、for 和 since 的区别与用法 【规则变化】 1. for + 时间段：表示动作或状态持续的一段时间。如：for three years (三年), for a long time (很长时间), for a few months (几个月)。 2. since + 过去的时间点：表示动作或状态从过去某个具体的时刻开始。如：since 2022 (自从2022年起), since last August (自从去年八月起), since yesterday (自从昨天起)。 3. since + 句子 (一般过去时)：引导时间状语从句，从句中的谓语动词必须用一般过去时。如：since he started working there (自从他开始在那里工作起)。 【易错点】 for 和 since 引导的时间状语可以互相转换。例如： He has lived here for 3 years. (假设现在是2025年) = He has lived here since 2022. = He has lived here since 3 years ago. (注意：since 后可以加 "时间段 + ago" 构成时间点)。 【例句】 I have been a member of the Red Cross for six years. 我成为红十字会成员已经六年了。 I have made a lot of friends since I joined the organization. 自从加入这个组织以来，我交了许多朋友。 三、短暂性（非延续性）动词与延续性动词的转换 【规则变化】 在肯定句中，短暂性动词（又称非延续性动词，如 buy, borrow, join, leave, die 等）表示的动作发生后瞬间就结束了，因此不能与 for 或 since 引导的时间段连用。 如果要表达持续的时间，必须将短暂性动词替换为相应的延续性动词或状态（be + 形容词/副词/介词短语）： 1. buy (买) → have / keep (拥有/保存) 2. borrow (借) → keep (保存) 3. join (加入) → be in / be a member of (是……的成员) 4. leave (离开) → be away (from) (离开状态) 5. die (死) → be dead (死亡状态) 6. begin / start (开始) → be on (进行状态) 7. catch a cold (感冒) → have a cold (患感冒状态) 【注意】 虽然短暂性动词在肯定句中不能与 for/since 连用，但在否定结构中，可用非延续性动词的现在完成时表示持续的状态。例如：I haven't bought any food since last week. (自从上周以来我没买过任何食物。) 【例句】 (误) He has joined the club for two years. (正) He has been in (或 been a member of) the club for two years. 他加入俱乐部两年了。 (误) I have borrowed this book since yesterday. (正) I have kept this book since yesterday. 我借这本书已经一天了。 二：单元语法知识练习 I. 单项选择（10道） 1. —_____ have you been a volunteer at the museum —For about two years. A. How long B. How soon C. How often D. How far 2. He _____ the youth group since last August. A. joined B. has joined C. is in D. has been a member of 3. The organization has trained over 6,000 vo ... ...