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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 volunteers ________ it began to offer classes.
A. for
B. since
C. in
D. from
4. I bought this English dictionary three years ago. That means I have ________ it for three years.
A. bought
B. borrowed
C. kept
D. had
5. —Have you ever ________ volunteer work
—Yes. I have been a volunteer ________ 2022.
A. did; for
B. do; since
C. doing; for
D. done; since
6. Mr. Wu has taught in a primary school as a volunteer ________ two years now.
A. in
B. for
C. since
D. during
7. The poor old man ________ for five years.
A. has been dead
B. has died
C. died
D. is dead
8. Because I was busy preparing for the exam, I ________ my grandparents since last month.
A. visited
B. didn't visit
C. have visited
D. haven't visited
9. My sister ________ a member of the Red Cross for six years.
A. is
B. was
C. has been
D. has become
10. They ________ many people in need since the charity ________.
A. have helped; began
B. helped; has begun
C. have helped; has begun
D. helped; began
II. 语法填空（3篇）
Passage 1
Teng Fei 11. ________ (be) a volunteer at a nursing home 12. ________ last year. He usually exercises with the 13. ________ (elder) to help them stay 14. ________ (act). Sometimes he 15. ________ (play) Chinese chess with them. He 16. ________ (even teach) some of them how to use a smart phone. He thinks it is a meaningful experience. He 17. ________ (make) a lot of friends 18. ________ he joined the youth group. The old people are always happy 19. ________ (see) him. Volunteering brings 20. ________ (he) a lot of joy and makes a difference in his life.
Passage 2
The Blue Sky Rescue is a famous volunteer organization. It 21. ________ (train) over 6,000 volunteers since it 22. ________ (begin) to offer classes three years 23. ________. Many young people 24. ________ (sign) up to be a volunteer recently. James is one of them. He 25. ________ (join) the organization in 2022. That means he has 26. ________ (be) a member 27. ________ about two years. He and his team members have 28. ________ (help) many people in need so far. James says, "I 29. ________ (not stop) helping others since I realized the 30. ________ (valuable) of volunteering."
Passage 3
Last summer holiday, Mary decided 31. ________ (do) some volunteer work. She went to an animal 32. ________ (shelter) in her neighborhood. She 33. ________ (work) there for several months now. At first, it was quite hard for her to handle the sick dogs. But she 34. ________ (not give) up. She has 35. ________ (learn) a lot about how to care for animals 36. ________ she went there. In fact, many homeless animals 37. ________ (save) by the shelter every year. Mary feels proud of 38. ________ (be) part of it. If everyone offers a helping hand, we can make a huge 39. ________ (different) to the world. A small act of kindness is 40. ________ (worth) a lot.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 volunteers ________ it began to offer classes.
A. for
B. since
C. in
D. from
4. I bought this English dictionary three years ago. That means I have ________ it for three years.
A. bought
B. borrowed
C. kept
D. had
5. —Have you ever ________ volunteer work
—Yes. I have been a volunteer ________ 2022.
A. did; for
B. do; since
C. doing; for
D. done; since
6. Mr. Wu has taught in a primary school as a volunteer ________ two years now.
A. in
B. for
C. since
D. during
7. The poor old man ________ for five years.
A. has been dead
B. has died
C. died
D. is dead
8. Because I was busy preparing for the exam, I ________ my grandparents since last month.
A. visited
B. didn't visit
C. have visited
D. haven't visited
9. My sister ________ a member of the Red Cross for six years.
A. is
B. was
C. has been
D. has become
10. They ________ many people in need since the charity ________.
A. have helped; began
B. helped; has begun
C. have helped; has begun
D. helped; began
II. 语法填空（3篇）
Passage 1
Teng Fei 11. ________ (be) a volunteer at a nursing home 12. ________ last year. He usually exercises with the 13. ________ (elder) to help them stay 14. ________ (act). Sometimes he 15. ________ (play) Chinese chess with them. He 16. ________ (even teach) some of them how to use a smart phone. He thinks it is a meaningful experience. He 17. ________ (make) a lot of friends 18. ________ he joined the youth group. The old people are always happy 19. ________ (see) him. Volunteering brings 20. ________ (he) a lot of joy and makes a difference in his life.
Passage 2
The Blue Sky Rescue is a famous volunteer organization. It 21. ________ (train) over 6,000 volunteers since it 22. ________ (begin) to offer classes three years 23. ________. Many young people 24. ________ (sign) up to be a volunteer recently. James is one of them. He 25. ________ (join) the organization in 2022. That means he has 26. ________ (be) a member 27. ________ about two years. He and his team members have 28. ________ (help) many people in need so far. James says, "I 29. ________ (not stop) helping others since I realized the 30. ________ (valuable) of volunteering."
Passage 3
Last summer holiday, Mary decided 31. ________ (do) some volunteer work. She went to an animal 32. ________ (shelter) in her neighborhood. She 33. ________ (work) there for several months now. At first, it was quite hard for her to handle the sick dogs. But she 34. ________ (not give) up. She has 35. ________ (learn) a lot about how to care for animals 36. ________ she went there. In fact, many homeless animals 37. ________ (save) by the shelter every year. Mary feels proud of 38. ________ (be) part of it. If everyone offers a helping hand, we can make a huge 39. ________ (different) to the world. A small act of kindness is 40. ________ (worth) a lot.
【参考答案与解析】
I. 单项选择
1.【答案】A
【解析】句意：——你在博物馆做志愿者多久了？——大概两年了。考查疑问词组辨析。根据答语 "For about two years" (表示时间段) 可知，提问动作持续了多长时间，必须用 How long。故选A。
2.【答案】D
【解析】句意：自从去年八月以来，他一直在这个青年团体里。考查现在完成时中非延续性动词的转换。since last August 提示用现在完成时，而 join (加入) 是瞬间发生的动作，不能和 since 连用，必须转变为延续性状态 has been a member of 或 has been in。故选D。
3.【答案】B
【解析】句意：该组织自开班以来，已培训了6000多名志愿者。考查现在完成时的时间状语。空后 "it began to offer classes" 是一个包含一般过去时的句子，表示动作发生的起点，必须用 since 引导。故选B。
4.【答案】D
【解析】句意：我是三年前买的这本英语词典。这意味着我已经拥有它三年了。考查短暂性动词的转换。buy 是非延续性动词，不能和 for three years 连用。其对应的延续性动词是 have 或 keep。此题表示“拥有”，用 had (have的过去分词)。故选D。
5.【答案】D
【解析】句意：——你曾经做过志愿者工作吗？——是的。自从2022年起我就一直是一名志愿者。考查现在完成时和介词。第一空，Have you ever + 过去分词 (done)；第二空，2022 是过去的时间点，需搭配 since。故选D。
6.【答案】B
【解析】句意：吴先生作为志愿者在小学任教至今已有两年了。考查介词的用法。two years 是时间段，现在完成时中接时间段必须用 for。故选B。
7.【答案】A
【解析】句意：这个可怜的老人已经去世五年了。考查短暂性动词的转换。die (死) 为短暂性动词，不能和 for five years 连用，必须换成状态 be dead。句子用现在完成时，即 has been dead。故选A。
8.【答案】D
【解析】句意：因为忙着准备考试，自从上个月以来我都没去看望过爷爷奶奶。考查现在完成时的否定结构。since last month 提示主句需用现在完成时。短暂性动词 (visit) 在否定句中可以和 since 连用，表示持续的状态。故选D。
9.【答案】C
【解析】句意：我妹妹成为红十字会成员已经六年了。考查现在完成时。for six years 表示动作持续，需用现在完成时。become 是非延续性动词不能用，应转为状态 be (has been)。故选C。
10.【答案】A
【解析】句意：自从该慈善机构成立以来，他们已经帮助了许多需要帮助的人。考查 since 的复合句时态。since 引导的从句若用作时间状语，从句需用一般过去时 (began)，而主句需用现在完成时 (have helped)。故选A。
II. 语法填空
Passage 1 答案及解析：
11. has been。结合后文的时间状语，表示“一直是一名志愿者”，用现在完成时。
12. since。last year 是过去的时间点，表示从去年开始，用 since。
13. elderly。the elderly 是固定表达，指“老人们，长者”。
14. active。stay 为系动词，后接形容词作表语，保持“活跃的” active。
15. plays。Usually, sometimes 等频度副词提示此处描述经常性的动作，用一般现在时，主语 he 为第三人称单数，故填 plays。
16. has even taught。联系上下文，他作为志愿者对老人们产生的影响持续至今，且表示经验或已完成的事情，用现在完成时。teach 的过去分词为 taught。
17. has made。since 引导从句，主句必须用现在完成时，表示“交了许多朋友”。
18. since。后接一般过去时的句子(he joined...)，作为现在完成时的时间状语，填 since。
19. to see。be happy to do sth. 是固定用法，表示“很高兴做某事”。
20. him。动词 bring 之后作宾语，用代词宾格 him。
Passage 2 答案及解析：
21. has trained。since 引导时间状语从句，主句需要用现在完成时。
22. began。since 引导的时间状语从句中，谓语动词通常用一般过去时。
23. ago。three years ago 是具体的过去时间点，和从句的一般过去时搭配。
24. have signed。recently（最近）常与现在完成时连用，表示最近发生且对现在有影响的动作。
25. joined。in 2022 是明确的过去时间，因此用一般过去时。
26. been。在 has 之后使用过去分词 been，表示一直处于成员的“状态”。
27. for。about two years 是一段时间，现在完成时中接时间段必须用 for。
28. helped。have 后接动词的过去分词，构成现在完成时。
29. haven't stopped。since 引导从句，主句需用现在完成时。此处为否定结构。
30. value。the 之后需用名词形式，valuable 的名词为 value (价值)。
Passage 3 答案及解析：
31. to do。decide to do sth. 决定做某事，用不定式作宾语。
32. shelter。animal shelter 动物收容所，本单元核心词汇，单数即可。
33. has worked。for several months now 提示动作持续至今，用现在完成时。
34. didn't give。描述当时（At first）发生的事情，转折也发生在过去，用一般过去时否定式。
35. learnt / learned。has 后接过去分词构成现在完成时。
36. since。后跟一般过去时从句 "she went there"，主句为现在完成时，故填 since。
37. are saved。描述客观或经常发生的事实 (every year)，且动物是被救助，用一般现在时的被动语态。
38. being。介词 of 之后接动名词形式。
39. difference。make a difference 是固定搭配，意为“产生影响/带来改变”，需用名词 difference。
40. worth。be worth a lot 意为“有很大价值/很值得”，worth 在此处作形容词（介词性形容词）作表语。

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