Grammar Rule in 30 Seconds
Use 'Modal + be + Past Participle' to focus on what happens to an object when using words like can, must, or should.
- Always use 'be' in its base form after the modal: 'It can be fixed' (not 'is fixed').
- The main verb must be a past participle: 'The work should be done' (not 'do' or 'did').
- For negatives, put 'not' between the modal and 'be': 'It cannot be opened'.
Overview
be动词和past participle（过去分词）。很多同学在学习时，往往因为中文里没有动词变位和被动标记的强迫性，而忽略了英语中那个关键的be。比如，你想说“这个项目必须在周五前完成”，如果你直接说 The project must finish by Friday，意思就变成了“项目自己去完成某事”，这在逻辑上是错误的。正确说法是 The project must be finished by Friday。通过学习这一课，你将学会如何准确地在英语中表达“可能性”、“必要性”或“建议”，同时保持句子的客观性。can, must, should, might 等，用来表达说话人的态度，比如能力、义务、可能性或建议。而被动语态的核心在于 be + past participle。当两者结合时，规则非常简单：情态动词后面必须跟动词原形，所以 be 永远保持原形，后面接过去分词。be 动词在这里充当了“被动标记”的角色，而 past participle 则承载了动作的具体含义。无论主语是单数还是复数，be 永远是 be，不会变成 is、are 或 was。这其实比中文更简单，因为你不需要考虑主语的人称变化。这种结构在职场中非常有用，比如在微信工作群里，你可以说 The report should be sent to the manager（报告应该被发给经理），这比直接指责某人 You should send the report 要委婉得多，这就是英语中“被动语态”带来的礼貌感和客观感。Subject + Modal Verb + be + Past Participle。无论你使用哪种情态动词，be 永远不会变。以下是详细的结构表：The room |must |be + 过去分词 | be cleaned |by tomorrow |can | 可能性/能力 | can be done | 可以被做 |must | 必须 | must be done | 必须被做 |should | 建议 | should be done | 应该被做 |might | 可能性 | might be done | 可能被做 |- 1当你不知道或者不需要提及动作执行者时：例如，在办公室看到打印机坏了，你可以说
The printer should be fixed（打印机应该被修一下），你不需要纠结是谁弄坏的，重点在于“打印机需要修理”这一事实。 - 2为了保持礼貌和委婉：在大学校园或职场中，直接批评别人
You made a mistake（你犯了个错）太生硬了。使用被动语态说A mistake has been made（一个错误被犯下了）或者The rules should be followed（规则应该被遵守），听起来会温和得多，不会让人感到被冒犯。 - 3在正式文档和说明中：当你写淘宝店铺的退换货政策或公司规章时，使用被动语态会显得非常专业。例如：
Returns can be accepted within 7 days（7天内可以接受退货），这比You can return items in 7 days听起来更像是一个正式的规定。
- 1遗漏
be动词：这是最常见的错误。因为中文里没有be动词，我们的大脑习惯直接跳过。例如：The work must done。这是错误的，因为must后面必须接动词原形，而done是过去分词。正确的是The work must be done。 - 2混淆过去分词和原形：很多同学会写
The report should be write。原因是在中文里，动词没有形态变化，我们容易下意识地使用动词原形。要记住：在被动语态里，动词必须变成past participle（如written,done,seen）。 - 3主动与被动逻辑混乱：受中文“把字句”和“被字句”的影响，有时会混淆主语。比如想说“这首歌应该被唱”，却说成了
This song should sing。这在英语里意思变成了“这首歌应该去唱歌”，显然不符合逻辑。一定要检查主语是不是动作的承受者。
We must finish the project. | 强调“我们”的责任 |The project must be finished. | 强调“项目”的状态 |The project is finished. | 强调事实状态 |The project must be finished. | 强调必要性/义务 |- 1问：
be动词在所有情态动词后都不变吗？
can, should, must 还是 might，后面接的永远是 be，绝对不能变成 is 或 are。- 1问：我可以用
get代替be吗？
get 可以用来表示被动（如 The work must get done），但在B1水平的考试和正式写作中，建议坚持使用 be，因为它更标准、更通用。- 1问：如果我想说出动作执行者，该怎么办？
by 这个介词。例如：The email should be sent by the manager。但请注意，如果不需要强调执行者，最好省略它，这样句子会更简洁。2. Negative Contractions
| Full Form | Contracted Form | Usage |
|---|---|---|
|
cannot be
|
can't be
|
Common in speech
|
|
should not be
|
shouldn't be
|
Common in speech
|
|
must not be
|
mustn't be
|
Common in speech/British English
|
|
will not be
|
won't be
|
Very common
|
|
could not be
|
couldn't be
|
Common in speech
|
|
might not be
|
mightn't be
|
Rare, mostly British
|
Modal Passive Structure
| Subject (Receiver) | Modal Verb | Auxiliary 'be' | Past Participle (V3) |
|---|---|---|---|
|
The work
|
can
|
be
|
done
|
|
The rules
|
must
|
be
|
followed
|
|
The letter
|
should
|
be
|
written
|
|
The house
|
might
|
be
|
sold
|
|
The truth
|
will
|
be
|
known
|
|
The decision
|
may
|
be
|
changed
|
|
The car
|
could
|
be
|
fixed
|
|
The laws
|
ought to
|
be
|
obeyed
|
Meanings
A grammatical construction used to express modality (possibility, necessity, obligation) while keeping the focus on the person or thing receiving the action rather than the one performing it.
Possibility/Ability
Expressing that an action is possible for the object.
“The problem can be solved easily.”
“A solution might be found soon.”
Obligation/Necessity
Expressing that an action is required or mandatory for the object.
“The law must be obeyed.”
“The taxes have to be paid by Friday.”
Permission/Prohibition
Expressing what is allowed or forbidden regarding the object.
“Phones may not be used during the exam.”
“The room can be rented for parties.”
Reference Table
| Form | Structure | Example |
|---|---|---|
|
Affirmative
|
Obj + Modal + be + V3
|
The cake will be eaten.
|
|
Negative
|
Obj + Modal + not + be + V3
|
The cake won't be eaten.
|
|
Question
|
Modal + Obj + be + V3?
|
Will the cake be eaten?
|
|
Short Answer (+)
|
Yes, Obj + Modal.
|
Yes, it will.
|
|
Short Answer (-)
|
No, Obj + Modal + not.
|
No, it won't.
|
|
With 'By' Agent
|
Obj + Modal + be + V3 + by...
|
The cake will be eaten by us.
|
|
Past Modal Passive
|
Obj + Modal + have been + V3
|
The cake should have been eaten.
|
正式程度
The report must be submitted by 5 PM. (Workplace deadline)
The report needs to be handed in by 5. (Workplace deadline)
The report's gotta be done by 5. (Workplace deadline)
Get that report in by 5, no cap. (Workplace deadline)
The Modal Passive Universe
Possibility
- Can be Ability
- Might be Uncertainty
Obligation
- Must be Strong necessity
- Should be Advice
Permission
- May be Formal permission
- Can be Informal permission
Active vs. Passive Modals
Is it Modal Passive?
Is there a modal (can, must, etc.)?
Is the focus on the receiver?
Did you add 'be'?
Common Past Participles for Passive
Regular
- • Finished
- • Cleaned
- • Fixed
- • Opened
Irregular
- • Done
- • Written
- • Seen
- • Taken
- • Broken
按水平分级的例句
The window can be opened.
It is possible to open the window.
The food must be hot.
The food needs to be hot.
The book can be read.
It is possible to read the book.
The car must be clean.
The car needs to be clean.
The room should be cleaned every day.
It is a good idea to clean the room daily.
The email can be sent now.
You are able to send the email now.
The door must not be locked.
Do not lock the door.
Can the bill be paid by credit card?
Is it possible to pay with a card?
The application must be submitted by Friday.
You are required to hand in the application by Friday.
The results might be announced tomorrow.
There is a chance they will tell us the results tomorrow.
This software can be downloaded for free.
You are able to get this software without paying.
The meeting should be rescheduled.
I suggest we change the time of the meeting.
The project ought to be completed ahead of schedule.
It is expected that the project will finish early.
Such behavior will not be tolerated in this office.
We will not allow this kind of behavior.
The data could be interpreted in several ways.
There are different ways to understand the data.
The contract may be terminated with 30 days' notice.
Either party can end the contract if they give notice.
It could be argued that the policy was a failure.
One might make the argument that the policy failed.
The implications must be carefully considered.
We need to think very deeply about the consequences.
No part of this book may be reproduced without permission.
You are not allowed to copy this book.
The witness should be questioned further.
It is necessary to ask the witness more questions.
The nuances of the text might be overlooked by a casual reader.
A normal reader might not notice the small details.
It is imperative that the status quo be maintained.
It is absolutely necessary that things stay as they are.
The debt shall be repaid in full by the end of the fiscal year.
The debt must be paid back completely.
The truth of the matter can only be surmised.
We can only guess what the truth is.
容易混淆
Learners often use the active form when they mean the passive because it's simpler.
They mean the same thing, but 'have to' conjugates like a normal verb.
Learners confuse 'be doing' with 'be done'.
常见错误
It can done.
It can be done.
It must be do.
It must be done.
The car can be fix.
The car can be fixed.
Must be the door closed?
Must the door be closed?
It should be not opened.
It should not be opened.
The letters can been sent.
The letters can be sent.
He can be tell.
He can be told.
The work must is done.
The work must be done.
It might be can fixed.
It might be fixed.
The house should be sell.
The house should be sold.
The task needs be done.
The task needs to be done.
It may be being processed.
It may be processed.
句型
The ___ must be ___ by ___.
It can be ___ easily.
___ should not be ___ without ___.
How can the ___ be ___?
Real World Usage
The successful candidate will be notified by email.
Hard hats must be worn on this site.
This issue can be resolved by restarting your device.
The mixture should be stirred until smooth.
This agreement may be modified only in writing.
Your account might be suspended if you break the rules.
The 'By' Test
Don't conjugate 'be'
Polite Complaints
Formal vs Informal
Smart Tips
Use 'should be' or 'could be' to make requests. It sounds less like a command.
Check if there is a modal before it. If so, you are looking at a modal passive!
Always use the 'third form' from your verb list (e.g., go-went-GONE).
Use 'must be' + V3. It is the standard way to express non-negotiable requirements.
发音
The 'be' reduction
In natural speech, the word 'be' is often unstressed and sounds like a quick /bi/ or even /bə/.
Modal + not contraction
Contractions like 'can't' or 'won't' are much more common than 'cannot' or 'will not' in spoken English.
Emphasis on the Modal
It MUST be done!
Conveys strong urgency or insistence.
Emphasis on the Participle
It can be FIXED.
Conveys that the action is possible, even if difficult.
记住它
记忆技巧
Remember 'MBP': Modal + Be + Participle. It's the 'Most Basic Passive' formula.
视觉联想
Imagine a robot on an assembly line. The robot doesn't care who built it, only that it 'must be built'. See the word 'BE' glowing in the middle of the robot's chest.
Rhyme
If a modal is what you see, don't forget the little word 'be'!
Story
A detective arrives at a crime scene. He doesn't know who did it, so he says: 'The door must be opened, the fingerprints must be taken, and the truth will be found.' He focuses on the actions because the 'who' is a mystery.
Word Web
挑战
Look around your room. Find 3 things and say what 'must be done' to them (e.g., 'The bed must be made', 'The window should be cleaned').
文化笔记
British speakers use 'mustn't be' more frequently than Americans, who often prefer 'shouldn't be' or 'can't be' for prohibitions.
The modal passive is used to avoid 'blame culture'. Instead of saying 'You didn't finish the report,' a manager says 'The report should have been finished,' focusing on the task.
Legal documents use 'shall be' to indicate a binding obligation, which is rarely used in everyday speech.
The passive voice in English evolved from Old English using 'weorthan' (to become) and 'beon' (to be). Modals were originally independent verbs that gradually became auxiliaries.
对话开场白
What is one thing in your city that should be improved?
Do you think AI can be used to replace teachers?
What rules must be followed in your workplace?
If you were president, what laws would be changed?
日记主题
常见错误
Test Yourself
The application form must ___ (sign) by the applicant.
Which sentence is correct?
Find and fix the mistake:
The secret should not be tell to anyone.
Active: You must wash this shirt by hand.
In the modal passive, the word 'be' changes to 'is' if the subject is singular (e.g., 'He').
A: Can I take this book home? B: No, it ___.
Select the valid structure:
Match each item on the left with its pair on the right:
Score: /8
练习题
8 exercisesThe application form must ___ (sign) by the applicant.
Which sentence is correct?
Find and fix the mistake:
The secret should not be tell to anyone.
Active: You must wash this shirt by hand.
In the modal passive, the word 'be' changes to 'is' if the subject is singular (e.g., 'He').
A: Can I take this book home? B: No, it ___.
Select the valid structure:
Match 'We can solve it' with its passive form.
Score: /8
Practice Bank
12 exercisesThis email ___ sent to the wrong person. Please retrieve it.
The new rules must explained clearly.
Choose the correct sentence:
Translate into English: 'El trabajo puede ser completado mañana.'
Arrange these words into a sentence:
Match the modals with their passive constructions:
These delicate items ___ handled with care.
Our flight could be delay due to the storm.
Translate into English: 'Las noticias serán anunciadas pronto.'
Arrange these words into a sentence:
Which of the following sentences is grammatically correct?
Connect the modals to their suitable passive completions:
Score: /12
常见问题 (8)
Yes, in informal English you can say 'It might get done,' but 'be' is much more common and safer for B1 learners.
English doesn't allow two modals together. You can't say 'It might can be done.' Use 'It might be possible to do it' instead.
No, in fact, we usually omit it if the person doing the action is obvious or not important.
Move the modal to the front: 'Can it be fixed?' or 'Should the meeting be moved?'
Because modal verbs are always followed by the base form of the next verb. The base form of 'is/am/are' is `be`.
Most can (can, could, must, should, may, might, will, would). 'Shall' is rare but possible in legal texts.
Technically, 'have to' is a semi-modal, but it follows the same passive pattern: 'have to + be + V3'.
Avoid it in very casual conversation with friends, as it can sound too formal or 'robotic'.
Scaffolded Practice
1
2
3
4
Mastery Progress
Needs Practice
Improving
Strong
Mastered
In Other Languages
puede ser + participio / se puede + infinitivo
English always requires the auxiliary 'be', whereas Spanish often uses the reflexive 'se'.
peut être + participe passé
French participles must agree in gender and number with the subject, unlike English.
kann ... werden + Partizip II
The auxiliary 'werden' and the modal create a 'verb bracket' where the participle goes to the very end of the sentence.
〜れる / 〜られる (passive suffix) + modal
Japanese doesn't use a separate 'be' verb; the passive is built into the main verb's conjugation.
Passive verb form + modal (yumkin/yajib)
There is no equivalent to the English 'be' auxiliary in Arabic passive constructions.
可以被 (kěyǐ bèi) + verb
Chinese verbs do not change form (no past participle), so the 'V3' concept is entirely new to Chinese learners.
Learning Path
Prerequisites
Learn These First
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