Modal Verbs — English Bac STM

ضمن برنامج بكالوريا STM

English carries a coefficient of 2 in the Bac Sciences et Technologies Mécaniques (STM) stream. The core subjects are Mathematics and Engineering Sciences (coefficient 7 each), then Physics-Chemistry (coefficient 5). English and Philosophy (coefficient 2) form the margin where candidate rankings and honours are settled. Mastering the structure of a piece of writing matters more here than memorising it.

في الامتحان

Three parts: Reading Comprehension, Language, and Writing (about 180 words). Reading technical drawings and function diagrams builds the same skill an essay needs: breaking an argument into parts and rebuilding it as a coherent plan.

أهداف التعلم

Apply this grammar point accurately in the Language section and in the guided writing of the Bac STM English exam (coefficient 2)
Distinguish can / could (ability, informal permission) from may / might (possibility, formal permission)
Distinguish must (obligation imposed by the speaker) from have to (obligation imposed by an outside rule)
Contrast must not (prohibition) with don't have to (absence of obligation)
Use must, can't and may / might / could to express a logical deduction

المفاهيم الأساسية

Ability, permission and possibility

can (present ability, informal permission), could (past ability, polite request), may / might (possibility, formal permission — might expresses a weaker possibility than may).

Obligation and advice

must (obligation the speaker imposes), have to (obligation an outside rule imposes); must not (prohibition) and don't have to (absence of obligation, the action is still allowed) are opposite meanings; should / ought to (advice, recommendation).

Logical deduction

must expresses a near-certain positive deduction (“He must be tired”), can't a certain negative deduction (“She can't be at home, the lights are off”), may / might / could an uncertain deduction, a mere possibility.

الأخطاء الشائعة

Confusing must not (prohibition) with don't have to (absence of obligation, the action is still allowed) — opposite meanings.

Adding to after a modal: “must to go” is wrong — must is always followed by the base form without to (have to is the exception, since have is the finite verb).

Using must for a deduction about the past without have: a past deduction is must have + past participle, not must + past participle.

مثال محلول

نص السؤال

Choose the right modal and justify: “The lights are off and the car isn't in the driveway. They ___ be at home.” (must / can't / should)

التصحيح

Weigh the evidence. Lights off and car gone are strong evidence that they are NOT at home.

Choose the right deduction. A certain negative deduction is marked by can't, not must (which would mean the opposite).

Result. “They can't be at home.” (must would mean “they must be at home”, which contradicts the evidence).

افهم الدرس، ثم تدرب.

ينشئ Orka تمارين غير محدودة وامتحانات تجريبية مصححة تغطي برنامج اللغة الإنجليزية في بكالوريا STM، مع تتبع تقدمك درساً بعد درس.

تابع مجاناً مع Orka

3 تمارين للتدرب

التمرين 1

Easy

Complete with must or mustn't: “You ___ smoke in the hospital, it's strictly forbidden.”

عرض التصحيح

mustn't — a formal prohibition, not an absence of obligation.

التمرين 2

Medium

Complete with have to or don't have to: “It's Saturday, so I ___ go to work today.”

عرض التصحيح

don't have to — absence of obligation (it is Saturday, going to work is not required), not a prohibition.

التمرين 3

Hard

Correct: “She must has finished the report by now.”

عرض التصحيح

A deduction about a completed fact is formed with must have + past participle: “She must have finished the report by now.”

تعمق أكثر في هذا الدرس

أكثر من 50 تمريناً تفاعلياً في هذا الدرس

تمارين يولدها الذكاء الاصطناعي ويصححها خطوة بخطوة حسب مستواك.

تسجيل الدخول مطلوب

اختبار ذكي متكيف

أسئلة تتكيف تلقائياً مع إجاباتك الصحيحة وأخطائك.

تسجيل الدخول مطلوب

تصحيح امتحانات سابقة مرتبطة بالدرس

مواضيع من الامتحانات الوطنية والجهوية السابقة.

تسجيل الدخول مطلوب

خطة مراجعة شخصية

ترتب أولوية هذا الدرس حسب تقدمك الحقيقي في الشعبة.

Premium

بطاقات مراجعة الدرس

الصيغ والتعريفات الأساسية لمراجعة سريعة.

Premium

مدرس ذكي بالدارجة

اطرح أسئلتك حول الدرس واحصل على شرح فوري.

Premium

الأسئلة الشائعة

must and have to — what is the real difference in the exam?

In meaning both express obligation, but must comes from the speaker (“I must call my mother”) and have to comes from an outside rule or authority (“I have to wear a uniform at school”). The Bac often accepts both in the affirmative but mostly tests their opposite forms in the negative.

How do I recognise a logical-deduction exercise?

The context gives clues (“the lights are off”, “she got an A”) from which you must conclude: must for a near-certain positive conclusion, can't for a certain negative conclusion, might / may / could for a mere possibility.

Can must be used in the past?

must itself has no past form for obligation (use had to); but for a deduction about a past fact, keep must and add have + past participle: must have finished, must have left.

English is far from my mechanical specialism — how do I approach it?

Treat it as a system with inputs and outputs: the input is a prompt, the processing is analysis then discussion, the output is a conclusion that settles the question. Learn that flow, apply it to the 31 chapters with two examples each, and one weekly session is enough to raise the mark.

Is this grammar point actually tested on the Bac STM English paper?

Yes — in the Language section as gap-fill, sentence-joining or error-correction, and indirectly in Writing, where the same structures decide whether a sentence is marked as accurate. One rule, two examples and one typical mistake per point is enough to cover both.