Mustn’t vs. Don’t have to – English Grammar Exercises for B1
Choose the best option (A, B, C, or D) to complete each sentence. Read the text carefully, as all questions are part of a continuous speech given by a company director to the project team.
“Welcome to the final briefing. Before we launch Project Alpha, we need to review your Non-Disclosure Agreements.”
1 You have all signed a legal contract, which means you ______ share any details of this project with people outside this room.
(a) don’t have to
(b) mustn’t
(c) mustn’t to
(d) shouldn’t
2 Under our strict company policy, employees ______ take any confidential physical documents home.
(a) aren’t have to
(b) don’t have to
(c) needn’t
(d) mustn’t
3 I will email you the exact statistical data later, so you ______ memorize these complex financial charts right now.
(a) don’t have to
(b) mustn’t
(c) shouldn’t
(d) don’t must
4 During the development phase, you ______ post any pictures of the prototype on your personal social media accounts.
(a) don’t have to
(b) couldn’t
(c) mustn’t
(d) mustn’t to
5 If a journalist randomly contacts you for a comment, you ______ answer their questions. Please direct them to the PR department.
(a) mustn’t
(b) don’t have to
(c) haven’t to
(d) won’t
6 For digital security reasons, you absolutely ______ leave your computer unlocked when you step away from your desk.
(a) don’t need
(b) mustn’t
(c) don’t have to
(d) mustn’t leaving
7 We are actually ahead of schedule, so the team ______ work overtime this weekend to finish the code.
(a) mustn’t
(b) don’t have to
(c) haven’t to
(d) shouldn’t
8 When eating lunch at public restaurants near the office, we ______ discuss the upcoming software features out loud.
(a) don’t have to
(b) mustn’t to
(c) mustn’t
(d) aren’t supposed
9 The IT security guidelines clearly state that you ______ copy any company files to personal USB drives.
(a) mustn’t
(b) don’t have to
(c) don’t must
(d) needn’t
10 The legal team has provided a 100-page manual, but you ______ read it all today; just focus on the one-page summary.
(a) mustn’t
(b) don’t have to
(c) shouldn’t
(d) not have to
11 Your electronic ID badge gives you access to the secure server room, so you ______ lose it under any circumstances!
(a) mustn’t
(b) don’t have to
(c) haven’t
(d) couldn’t
12 Due to the high-level security clearance, staff members ______ bring any friends or family members into the building.
(a) don’t have to
(b) mustn’t
(c) mustn’t to
(d) don’t need
13 As long as you are wearing your official laboratory coat, you ______ wear a formal business suit inside the testing facility.
(a) mustn’t
(b) shouldn’t
(c) don’t have to
(d) aren’t to
14 You ______ throw printed hardware designs into the regular trash bin; always use the heavy-duty paper shredder.
(a) don’t have to
(b) mustn’t throwing
(c) mustn’t
(d) shouldn’t
15 Even when collaborating with other authorized team members, you ______ share your personal login password.
(a) don’t have to
(b) don’t must
(c) wouldn’t
(d) mustn’t
16 If I send you an update email at 1:00 AM, you ______ reply immediately; I can wait until regular morning hours.
(a) mustn’t
(b) haven’t to
(c) shouldn’t
(d) don’t have to
17 To prevent cyber attacks, developers ______ attempt to bypass the company firewall for any reason.
(a) don’t have to
(b) mustn’t
(c) mustn’t to
(d) needn’t
18 When the project successfully concludes, you ______ keep any prototype devices; they must all be returned to the vault.
(a) don’t have to
(b) haven’t to
(c) mustn’t
(d) couldn’t
19 The marketing department will handle the main presentation, meaning you ______ prepare a speech for the press conference.
(a) don’t have to
(b) mustn’t
(c) haven’t to
(d) mustn’t prepare
20 I will say this one last time: you ______ breach this contract, or the company will terminate your employment and take immediate legal action.
(a) don’t have to
(b) don’t must
(c) mustn’t
(d) shouldn’t
ANSWER KEY & EXPLANATIONS
1 (b) mustn’t
- Why it is correct: Sharing details violates the NDA. It is a strict legal prohibition.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake (meaning “you aren’t forced to share, but you can,” which destroys the NDA). (c) “mustn’t to” is a Structural Error (modals do not take “to”). (d) “shouldn’t” is a Meaning Trap (too weak for a legal contract).
2 (d) mustn’t
- Why it is correct: Taking documents home is a breach of security rules. It is absolutely forbidden.
- Distractor Analysis: (b) “don’t have to” is a Common Mistake. (a) “aren’t have to” is a Structural Error. (c) “needn’t” is a Meaning Trap (indicates lack of necessity, not prohibition).
3 (a) don’t have to
- Why it is correct: The director will email the data, so the action of memorizing it is not necessary.
- Distractor Analysis: (b) “mustn’t” is a Common Mistake. (d) “don’t must” is a Structural Error. (c) “shouldn’t” is a Meaning Trap.
4 (c) mustn’t
- Why it is correct: Posting pictures leaks the product. This is strictly prohibited.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (d) “mustn’t to” is a Structural Error. (b) “couldn’t” is a Meaning Trap.
5 (a) mustn’t
- Why it is correct: Speaking to journalists without authorization is a severe policy violation.
- Distractor Analysis: (b) “don’t have to” is a Common Mistake (implies “you don’t have to answer, but you can,” which is legally dangerous). (c) “haven’t to” is a Structural Error. (d) “won’t” is a Meaning Trap.
6 (b) mustn’t
- Why it is correct: Leaving a PC unlocked is a direct security hazard. It is forbidden.
- Distractor Analysis: (c) “don’t have to” is a Common Mistake. (d) “mustn’t leaving” is a Structural Error (requires bare infinitive). (a) “don’t need” is a Structural Error (requires “to”).
7 (b) don’t have to
- Why it is correct: The team is ahead of schedule, removing the obligation to work on the weekend.
- Distractor Analysis: (a) “mustn’t” is a Common Mistake. (c) “haven’t to” is a Structural Error. (d) “shouldn’t” is a Meaning Trap.
8 (c) mustn’t
- Why it is correct: Discussing secrets in public exposes the company. It is prohibited.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (b) “mustn’t to” is a Structural Error. (d) “aren’t supposed” is a Structural Error (needs “to discuss”).
9 (a) mustn’t
- Why it is correct: Copying files to personal drives is data theft. It is strictly forbidden.
- Distractor Analysis: (b) “don’t have to” is a Common Mistake. (c) “don’t must” is a Structural Error. (d) “needn’t” is a Meaning Trap.
10 (b) don’t have to
- Why it is correct: Reading all 100 pages today is not an obligation because there is a summary.
- Distractor Analysis: (a) “mustn’t” is a Common Mistake. (d) “not have to” is a Structural Error. (c) “shouldn’t” is a Meaning Trap.
11 (a) mustn’t
- Why it is correct: Losing the badge compromises building security. You are forbidden to let this happen.
- Distractor Analysis: (b) “don’t have to” is a Common Mistake (implies “you don’t need to lose it, but you can”). (c) “haven’t” is a Structural Error. (d) “couldn’t” is a Meaning Trap.
12 (b) mustn’t
- Why it is correct: Bringing unauthorized guests into a secure facility is prohibited.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (c) “mustn’t to” is a Structural Error. (d) “don’t need” is a Structural Error (needs “to”).
13 (c) don’t have to
- Why it is correct: The lab coat replaces the suit, so the obligation to wear formal clothes is removed.
- Distractor Analysis: (a) “mustn’t” is a Common Mistake. (d) “aren’t to” is a Structural Error. (b) “shouldn’t” is a Meaning Trap.
14 (c) mustn’t
- Why it is correct: Throwing documents in the normal trash is a security breach. It is forbidden.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (b) “mustn’t throwing” is a Structural Error. (d) “shouldn’t” is a Meaning Trap.
15 (d) mustn’t
- Why it is correct: Sharing passwords is an absolute violation of IT policy.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (b) “don’t must” is a Structural Error. (c) “wouldn’t” is a Meaning Trap.
16 (d) don’t have to
- Why it is correct: Replying after midnight is not required. You lack the obligation to do it immediately.
- Distractor Analysis: (a) “mustn’t” is a Common Mistake. (b) “haven’t to” is a Structural Error. (c) “shouldn’t” is a Meaning Trap.
17 (b) mustn’t
- Why it is correct: Bypassing a firewall is a severe cyber-security violation. It is strictly prohibited.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (c) “mustn’t to” is a Structural Error. (d) “needn’t” is a Meaning Trap.
18 (c) mustn’t
- Why it is correct: Keeping company property is essentially theft. It is forbidden.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (b) “haven’t to” is a Structural Error. (d) “couldn’t” is a Meaning Trap.
19 (a) don’t have to
- Why it is correct: Since the PR team is doing it, the developers are freed from the obligation of writing a speech.
- Distractor Analysis: (b) “mustn’t” is a Common Mistake. (d) “mustn’t prepare” is a Meaning Trap (it means they are forbidden from preparing a speech, which is unlikely; they just aren’t required to). (c) “haven’t to” is a Structural Error.
20 (c) mustn’t
- Why it is correct: Breaching the contract results in termination. It is the ultimate legal prohibition.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake (using this here would sound like a joke: “You don’t have to break the law”). (b) “don’t must” is a Structural Error. (d) “shouldn’t” is a Meaning Trap (far too weak for a lawsuit warning).
GRAMMAR POINTS TO REMEMBER
1 MUSTN’T (The Absolute Legal Prohibition):
- Meaning: It is strictly forbidden. In a corporate or legal environment (like an NDA), doing this action will result in severe consequences, such as getting fired or sued. You have zero permission.
- Corporate Examples: You mustn’t leak secrets. You mustn’t share passwords. You mustn’t talk to the press.
- Structure: Subject + mustn’t + Verb (bare infinitive). (Never use “to”).
2 DON’T HAVE TO (The Absence of Obligation):
- Meaning: It is NOT necessary. You are not forced to do it. The company does not require this action from you.
- Corporate Examples: You don’t have to work overtime (we are ahead of schedule). You don’t have to memorize the data (it’s in the email).
- Structure: Subject + don’t/doesn’t have to + Verb (bare infinitive).
The NDA Rule of Thumb: If doing the action gets you fired, use MUSTN’T. If doing the action just means you are wasting your own time (because it’s not required), use DON’T HAVE TO.