Modal Verbs

Respuesta correcta: A) mustn't

• A) mustn't'Mustn't' is the modal of prohibition in the present, so it states that using the phone is not allowed during the test.
• B) might not'Might not' only suggests a small possibility. The posted rule forbids the action completely, so it needs the strongest modal.
• C) don't have to'Don't have to' means an action is not required but still allowed, whereas the teacher's rule removes the permission entirely.
• D) should not'Should not' advises against the action and leaves the choice to the student, but a posted school rule is a prohibition.

Respuesta correcta: B) A possibility that is not certain

• A) A certainty about the weatherA certainty would be expressed with 'must'. 'Might' leaves the outcome open, which is the point of the sentence.
• B) A possibility that is not certain'Might' presents the rain as possible but not certain, so the speaker avoids committing to a forecast.
• C) A rule that forbids going outNothing in the sentence forbids anything. A prohibition would need 'mightn't' in a different context.
• D) A past event that did not happenThe afternoon is still ahead, so the sentence is about the future. A missed past event needs 'might have'.

Respuesta correcta: C) To express a deduction from evidence

• A) To give the reader an orderThe writer is not instructing the reader to do anything. The word follows a reason, so it reports a conclusion instead.
• B) To forbid the presentationNothing is prohibited in this sentence. A prohibition would require the negative form 'must not'.
• C) To express a deduction from evidenceThe hours in the library are the evidence, and 'must' shows how certain the writer is about the conclusion.
• D) To promise a future resultThere is no promise about what will happen. The sentence reasons backwards from a sign to a probable explanation.

Respuesta correcta: B) could

• A) can'Can' describes an ability the person still has, and the sentence says she has lost that ability in the present.
• B) could'Could' is the past form of 'can', so it describes the ability she had as a child and no longer has.
• C) must'Must' expresses obligation or deduction, never an ability that somebody had in the past.
• D) will'Will' speaks about the future, so it cannot describe what she was able to do when she was five.

Respuesta correcta: D) 'Must' is a strong obligation and 'should' is advice

• A) Both sentences express the same obligationThe two modals differ in strength: one advises and the other imposes, so they are not equivalent.
• B) 'Must' is the weaker of the two modalsThe order is the other way round. 'Must' states an obligation, and 'should' only offers advice.
• C) 'Should' forbids the listener from goingA prohibition would need 'shouldn't'. The positive form 'should' recommends an action without banning it.
• D) 'Must' is a strong obligation and 'should' is advice'Must' obliges the listener to act, while 'should' recommends an action that the listener may ignore.

Respuesta correcta: C) mustn't

• A) shouldn't'Shouldn't' gives advice, so the sentence would read as a recommendation. The context needs a word that forbids the action outright.
• B) can't'Can't' here would describe an ability the person does not have, not a rule that applies to everybody in the laboratory.
• C) mustn't'Mustn't' is the modal of prohibition in the present, so it states that the action is not allowed at all.
• D) mightn't'Mightn't' expresses a small possibility, which is far too weak for something described as dangerous.

Respuesta correcta: B) Present obligation

• A) A past actionNothing in the sentence refers to the past. A past obligation would be expressed with 'had to finish'.
• B) Present obligation'Must' followed by a bare infinitive states an obligation the speaker has now, in the present.
• C) Past obligationA past obligation uses 'had to', as in 'I had to finish it'. 'Must' in this sentence points to the present.
• D) A possibility'Must' never expresses chance. Possibility is given by 'may', 'might' or 'could'.

Respuesta correcta: C) To express a deduction from evidence

• A) To give an orderThe writer is not ordering the listener to do anything. The word follows a reason, so it reports a conclusion.
• B) To make a promiseThere is no promise about a future action. 'Must' here draws a conclusion from the long experience described.
• C) To express a deduction from evidenceThe twelve years of work are the evidence, and 'must' reports the strong conclusion the writer draws from it.
• D) To express a prohibitionNothing is forbidden in this sentence. A prohibition would need 'mustn't', but 'must' is used positively here.

Respuesta correcta: D) Advice or recommendation

• A) A rule that is always brokenThe word describes advice, not a broken rule. Breaching a rule would require 'mustn't', which forbids rather than advises.
• B) A past event that did not happenThe sentence gives advice for the present and the future. A missed past action is expressed with 'should have'.
• C) A fact that everybody agrees onThe speaker is advising the listener, so the statement is a recommendation rather than shared information.
• D) Advice or recommendation'Should' gives advice about what is a good idea to do, which fits a suggestion to see a doctor.

Respuesta correcta: A) mustn't

• A) mustn't'Mustn't' is the modal of prohibition, so it states that opening the windows is forbidden during the test.
• B) shouldn't'Shouldn't' only advises against the action. The stem says the rule is absolute, which points to a full prohibition.
• C) mightn't'Mightn't' suggests a small possibility, so it would be much too weak for a rule described as absolute.
• D) don't have to'Don't have to' means an action is not required, but it still allows the action. That is not the same as forbidding it.

Respuesta correcta: B) Students don't have to bring a water bottle and mustn't bring food.

• A) Students must bring a water bottle and mustn't bring food.The notice says the bottle is allowed, not required, so 'must' overstates the first rule and only the second half is right.
• B) Students don't have to bring a water bottle and mustn't bring food.'Don't have to' reports that the bottle is optional while 'mustn't' reports that food is forbidden, matching the two rules.
• C) Students mustn't bring a water bottle and mustn't bring food.Both halves here are prohibitions, but the bottle is permitted, so the first rule is reported wrongly.
• D) Students don't have to bring a water bottle and shouldn't bring food.The first half is right, but 'shouldn't' only advises against food when the notice actually forbids it.

Respuesta correcta: C) A strong deduction about the past

• A) An obligation to park outsideAn obligation to do that earlier would use 'had to park'. Here the speaker is drawing a conclusion from the evidence.
• B) Permission to park outsidePermission would use 'might have' or 'was allowed to'. The sentence reports an inference, not a permission.
• C) A strong deduction about the past'Must have' plus a past participle reports a conclusion the speaker is sure about, based on the dry road and the wet tyres.
• D) Proof that somebody watched the carNobody observed the car. The evidence is indirect, so the sentence shows an inference rather than direct observation.

Respuesta correcta: D) Must

• A) Could'Could' is one of the weakest modals of deduction, since it keeps the possibility of a different explanation open.
• B) Might'Might' is weaker than 'must' because it offers the conclusion as a possibility rather than as a certainty.
• C) Should'Should' gives advice or an expectation, so it does not claim that the speaker knows the explanation for certain.
• D) Must'Must' is the strongest of the modals of deduction, because the speaker presents the conclusion as almost certain.

Respuesta correcta: C) Regret about a missed action in the past

• A) An obligation for the futureA future obligation is simply 'should' with a bare infinitive. The sentence looks back at an action that did not happen.
• B) A prohibition in the pastA prohibition would need 'shouldn't have'. Here 'should' is positive, so the focus is a missed action and not a rule.
• C) Regret about a missed action in the past'Should have' plus a past participle points to an action that was advisable in the past but did not occur.
• D) A doubt about a future planThe sentence is about an umbrella that was not taken, which is a past situation rather than a future plan.

Respuesta correcta: B) A possibility that is not certain

• A) A rule that forbids the meetingA prohibition would be 'mightn't' or 'mustn't'. The sentence presents the starting time as uncertain, not forbidden.
• B) A possibility that is not certain'Might' presents something as possible but not certain, which is why the speaker avoids promising nine o'clock.
• C) An obligation to hold the meetingAn obligation would use 'must'. Here the speaker is uncertain, so the modal expresses possibility instead.
• D) A past event that did not happenThe meeting refers to the future. A past unreal situation needs 'might have' plus a past participle.

Respuesta correcta: C) You don't have to bring a calculator, and you mustn't use a phone during the test.

• A) You mustn't bring a calculator, and you don't have to use a phone during the test.This prohibits the optional calculator and treats the forbidden phone as merely unnecessary, reversing both meanings.
• B) You must bring a calculator, and you may use a phone during the test.'Must' makes the calculator compulsory, and 'may' permits phone use; neither matches the notice.
• C) You don't have to bring a calculator, and you mustn't use a phone during the test.'Don't have to' expresses absence of obligation, while 'mustn't' expresses prohibition.
• D) You may bring a calculator, and you should use a phone during the test.The calculator permission fits, but 'should' recommends phone use even though the notice forbids it.

Respuesta correcta: C) A strong inference about a completed action based on present evidence.

• A) A past obligation imposed on the students.A past obligation would normally use 'had to leave'; here the speaker draws a conclusion from evidence.
• B) Permission for the students to leave in the future.Permission could use 'may leave', whereas 'must have left' refers to an inferred completed action.
• C) A strong inference about a completed action based on present evidence.'Must have' plus a past participle expresses a strong deduction about the past; the locked door and darkness supply evidence.
• D) Proof that the speaker personally watched the students leave.The sentence describes indirect evidence and a deduction, not direct observation of the departure.

Respuesta correcta: C) Borrowing up to three books is allowed, but returning them is required

• A) Borrowing three books is forbiddenThe text permits up to three books with 'may', so reading the borrowing as forbidden reverses the first rule.
• B) Borrowing three books is mandatory'May' grants permission, so the borrowing is allowed rather than compulsory. Nothing in the text makes it a duty.
• C) Borrowing up to three books is allowed, but returning them is required'May' gives permission for up to three books and 'must' requires the return on the same day.
• D) Borrowing is allowed and returning them is optionalThe second rule is wrong: 'must' requires the return, so it is not optional as this option claims.

Respuesta correcta: D) could

• A) can'Can' describes an ability the person still has, and the sentence says she has lost that ability.
• B) must'Must' expresses obligation or deduction, never an ability that somebody had in the past.
• C) will'Will' speaks about the future, so it cannot describe what she was able to do as a teenager.
• D) could'Could' is the past form of 'can', so it describes the ability she had then and does not have now.

Respuesta correcta: B) Can you close the window, please?

• A) She can swim four hundred metres.This sentence reports an ability she has, and there is no request directed at the listener.
• B) Can you close the window, please?Correct! 'Can you...' is the polite request form. It does not ask what the listener is able to do; it asks for an action.
• C) He can play the guitar, but he cannot read music.Both halves of this sentence describe abilities, so 'can' states what people are able to do.
• D) The machine can fail when the power goes out.Here 'can' describes something that is possible, that is the possibility of a breakdown, and not a request.