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 conversation carefully, as all questions are part of a continuous plan to organize a secret birthday party for a friend.
1 We are organizing a huge surprise party for Emma, so you ______ tell her anything about it!
(a) don’t have to
(b) mustn’t to
(c) mustn’t
(d) haven’t to
2 This is a top-secret mission. You ______ breathe a single word to anyone in our class.
(a) mustn’t
(b) don’t must
(c) don’t have to
(d) shouldn’t
3 I have already bought all the decorations, so you ______ buy any balloons.
(a) shouldn’t
(b) don’t have to
(c) mustn’t
(d) haven’t to
4 Emma is arriving exactly at 7 PM. We ______ be late for our own surprise!
(a) mustn’t
(b) don’t have to
(c) mustn’t being
(d) haven’t
5 You ______ wrap her present right now; we have plenty of time to do it tomorrow morning.
(a) don’t have
(b) mustn’t
(c) not have to
(d) don’t have to
6 Remember, you ______ act suspicious or nervous when you see her at school today.
(a) needn’t to
(b) mustn’t
(c) don’t have to
(d) mustn’t to act
7 If she asks why we are cleaning the house, you ______ give her the real reason.
(a) don’t have to
(b) shouldn’t
(c) mustn’t
(d) don’t must
8 We have ordered plenty of pizzas, meaning you ______ bring any extra food unless you really want to.
(a) don’t have to
(b) mustn’t
(c) haven’t to
(d) don’t need
9 The golden rule of this entire plan is that she ______ find out before she opens the front door.
(a) doesn’t have to
(b) mustn’t
(c) hasn’t to
(d) doesn’t must
10 You ______ pretend to forget her birthday completely; just say “Happy Birthday” and play it cool.
(a) mustn’t
(b) don’t have to
(c) hadn’t to
(d) don’t have
11 I will personally drive to the bakery to pick up the cake, so you ______ worry about it.
(a) haven’t to
(b) mustn’t
(c) don’t have to
(d) not must
12 However, you ______ forget to pick up the special sparkler candles I ordered online!
(a) don’t have to
(b) mustn’t forgetting
(c) haven’t to
(d) mustn’t
13 We ______ leave any receipts for the party supplies lying around on the living room table.
(a) mustn’t
(b) don’t have to
(c) shouldn’t
(d) don’t must
14 The guests ______ park their cars in front of the house, or she will recognize them immediately!
(a) mustn’t to
(b) mustn’t
(c) don’t have to
(d) haven’t to
15 You can invite your sister if you want, but she ______ post anything about it on social media yet.
(a) doesn’t have to
(b) mustn’t posts
(c) mustn’t
(d) needn’t
16 Everyone ______ dress up formally; casual clothes are perfectly fine for this kind of house party.
(a) doesn’t have to
(b) mustn’t
(c) don’t have to
(d) haven’t to
17 It is absolutely crucial that we ______ make any loud noises while we are hiding in the dark.
(a) don’t have to
(b) needn’t
(c) mustn’t
(d) mustn’t making
18 We ______ hire a professional DJ because I have already prepared a great dance playlist on my phone.
(a) mustn’t
(b) haven’t to
(c) don’t have to
(d) aren’t have to
19 You ______ text her at exactly midnight, as long as you act normally when you see her tomorrow.
(a) mustn’t
(b) aren’t to
(c) can’t
(d) don’t have to
20 Above all, you ______ ruin this surprise! She has had a tough year and really deserves this joy.
(a) shouldn’t
(b) don’t have to
(c) mustn’t
(d) don’t must
ANSWER KEY & EXPLANATIONS
1 (c) mustn’t
- Explanation: Revealing the party will ruin the plan. It is a strict prohibition.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake (meaning you are not obliged to tell her, but you can if you want – which destroys the secret). (b) “mustn’t to” is a Structural Error (must is followed by a bare infinitive, no “to”). (d) “haven’t to” is a Meaning Trap/Structural Error.
2 (a) mustn’t
- Explanation: “Breathe a word” means to tell a secret. Doing so is forbidden.
- Distractor Analysis: (c) “don’t have to” is a Common Mistake. (b) “don’t must” is a Structural Error (the negative of must is mustn’t). (d) “shouldn’t” is a Meaning Trap (too weak for a “top-secret mission”).
3 (b) don’t have to
- Explanation: The balloons are already bought, so buying more is unnecessary, but not strictly forbidden. It is a lack of obligation.
- Distractor Analysis: (c) “mustn’t” is a Common Mistake. (a) “shouldn’t” is a Meaning Trap. (d) “haven’t to” is a Structural Error.
4 (a) mustn’t
- Explanation: Being late to your own surprise party ruins the event. It is a strong negative obligation.
- Distractor Analysis: (b) “don’t have to” is a Common Mistake. (c) “mustn’t being” is a Structural Error (needs bare infinitive “be”). (d) “haven’t” is a Structural Error.
5 (d) don’t have to
- Explanation: Wrapping the present now is not necessary because there is time tomorrow. You can do it if you want, but there is no pressure.
- Distractor Analysis: (b) “mustn’t” is a Common Mistake. (a) “don’t have” is a Structural Error (missing “to”). (c) “not have to” is grammatically incorrect.
6 (b) mustn’t
- Explanation: Acting suspicious will give away the secret. It is prohibited.
- Distractor Analysis: (c) “don’t have to” is a Common Mistake. (d) “mustn’t to act” is a Structural Error. (a) “needn’t to” is a Structural Error (needn’t is followed by bare infinitive, no “to”).
7 (c) mustn’t
- Explanation: Giving the real reason breaks the secret. You are forbidden to do it.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake (implies you can tell the truth if you feel like it, which is wrong). (b) “shouldn’t” is a Meaning Trap. (d) “don’t must” is a Structural Error.
8 (a) don’t have to
- Explanation: Bringing extra food is optional because there is already plenty.
- Distractor Analysis: (b) “mustn’t” is a Common Mistake. (d) “don’t need” is a Structural Error (requires “to” -> “don’t need to”). (c) “haven’t to” is a Structural Error.
9 (b) mustn’t
- Explanation: Finding out before the door opens is exactly what must be prevented.
- Distractor Analysis: (a) “doesn’t have to” is a Common Mistake. (d) “doesn’t must” is a Structural Error. (c) “hasn’t to” is a Structural Error.
10 (b) don’t have to
- Explanation: It is not necessary to be mean and completely forget her birthday. You have a choice to just say “Happy Birthday” normally.
- Distractor Analysis: (a) “mustn’t” is a Common Mistake. (d) “don’t have” is a Structural Error (missing “to”). (c) “hadn’t to” is a Structural Error.
11 (c) don’t have to
- Explanation: The speaker is taking care of the cake, removing the necessity/obligation for the listener to worry about it.
- Distractor Analysis: (b) “mustn’t” is a Common Mistake. (a) “haven’t to” is a Structural Error. (d) “not must” is a Structural Error.
12 (d) mustn’t
- Explanation: Forgetting the candles is a bad thing that must be avoided.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (b) “mustn’t forgetting” is a Structural Error (needs bare verb). (c) “haven’t to” is a Structural Error.
13 (a) mustn’t
- Explanation: Leaving receipts will expose the surprise. It is strictly forbidden.
- Distractor Analysis: (b) “don’t have to” is a Common Mistake. (c) “shouldn’t” is a Meaning Trap (it’s good advice, but “mustn’t” fits the strict rule of a surprise plan better). (d) “don’t must” is a Structural Error.
14 (b) mustn’t
- Explanation: If guests park outside, the surprise is ruined. They are strictly prohibited from doing so.
- Distractor Analysis: (c) “don’t have to” is a Common Mistake (means they can park there if they want, which ruins everything). (a) “mustn’t to” is a Structural Error. (d) “haven’t to” is a Structural Error.
15 (c) mustn’t
- Explanation: Posting on social media before the party will leak the secret to Emma.
- Distractor Analysis: (a) “doesn’t have to” is a Common Mistake. (b) “mustn’t posts” is a Structural Error (mustn’t + bare infinitive ‘post’, no ‘s’). (d) “needn’t” is a Meaning Trap (means lack of obligation, not prohibition).
16 (a) doesn’t have to
- Explanation: Dressing up is not required; casual clothes are fine. Note the grammar: “Everyone” is a singular pronoun.
- Distractor Analysis: (c) “don’t have to” is a Structural Error (“Everyone” takes a singular verb “doesn’t”). (b) “mustn’t” is a Common Mistake. (d) “haven’t to” is a Structural Error.
17 (c) mustn’t
- Explanation: Making noise in the dark will ruin the surprise jump.
- Distractor Analysis: (a) “don’t have to” is a Common Mistake. (d) “mustn’t making” is a Structural Error. (b) “needn’t” is a Meaning Trap.
18 (c) don’t have to
- Explanation: The playlist is ready, so hiring a DJ is unnecessary (lack of obligation).
- Distractor Analysis: (a) “mustn’t” is a Common Mistake. (b) “haven’t to hire” is a Structural Error. (d) “aren’t have to” is a Structural Error.
19 (d) don’t have to
- Explanation: Texting at midnight is not a requirement for the plan to work.
- Distractor Analysis: (a) “mustn’t” is a Common Mistake (texting at midnight doesn’t ruin the surprise if you act normal). (c) “can’t” is a Meaning Trap. (b) “aren’t to” is a Structural Error.
20 (c) mustn’t
- Explanation: Ruining the surprise is the ultimate thing you are forbidden to do.
- Distractor Analysis: (b) “don’t have to” is a Common Mistake. (a) “shouldn’t” is a Meaning Trap (too weak). (d) “don’t must” is a Structural Error.
GRAMMAR POINTS TO REMEMBER
1 MUSTN’T (Prohibition):
- Meaning: Do not do this. It is a bad idea, against the rules, or it will ruin our plans! You have NO choice.
- Context in a Surprise Party: You mustn’t tell the birthday girl, you mustn’t act suspicious, and you mustn’t leave evidence. If you do these things, the surprise is destroyed.
- Structure: Subject + mustn’t + Verb (bare infinitive). (Never use “to” after mustn’t).
2 DON’T HAVE TO (Lack of Obligation):
- Meaning: It is not necessary to do this. However, if you really want to do it, you can. It won’t hurt the plan.
- Context in a Surprise Party: You don’t have to bring food (we have enough, but if you bring a cake, that’s fine). You don’t have to wear a suit (but you can if you like).
- Structure: Subject + don’t/doesn’t have to + Verb (bare infinitive).
The Golden Rule: If doing the action ruins the secret, use MUSTN’T.
If doing the action is just unnecessary but harmless, use DON’T HAVE TO.