English grammar worksheet focusing on modals of obligation, lack of necessity, and prohibition.

Let's go through Activity 11 step by step, solving each section with explanations.

---

A. Complete the following sentences with “mustn’t” or “don’t have to.”

We need to understand the difference between:
- mustn’t = prohibition (you are not allowed to do something)
- don’t have to = lack of necessity (you are allowed not to do it, but you can if you want)

#### 1. The museum is free. You ______ pay for the entrance.
✔ don’t have to
→ It’s not necessary to pay because it’s free.
✘ *mustn’t* would mean "you're not allowed to pay", which doesn't make sense here.

#### 2. You have to wear a uniform at school. You ______ wear blue jeans.
✔ mustn’t
→ Wearing blue jeans is not allowed (prohibited) because you must wear a uniform.
✘ *don’t have to* would mean "you don’t need to", but that’s not the same as being forbidden.

#### 3. The speed limit is 90 km per hour. You ______ drive faster.
✔ mustn’t
→ Driving faster than 90 km/h is illegal, so it's prohibited.

#### 4. You live in a very small place. You ______ clean it every day. Just clean it twice.
✔ don’t have to
→ Cleaning daily is not required, only twice is enough.

#### 5. Your job is from Monday to Friday. You ______ come on weekends.
✔ don’t have to
→ It’s not necessary to work on weekends; your job is only Mon–Fri.

#### 6. That river is extremely dangerous. You ______ swim in it.
✔ mustn’t
→ Swimming is dangerous and forbidden — it’s a safety rule.

---

✔ A Answers:

1. don’t have to
2. mustn’t
3. mustn’t
4. don’t have to
5. don’t have to
6. mustn’t

---

B. Choose the correct option.

Now we use:
- have to / has to = obligation (external rules, duties)
- must = strong obligation, often internal or formal rules
- don’t have to / doesn’t have to = no obligation
- mustn’t = prohibition

#### 1) She DON’T HAVE TO / DOESN’T HAVE TO / MUST wash the dishes now. I’ll do it later.
✔ doesn’t have to
→ Correct form: subject + auxiliary verb (does) + not + have to.
✘ "Don’t have to" is incorrect with "she" (needs auxiliary).
✘ "must" means she must wash them, but the sentence says she won’t.

#### 2) My brother HAVE TO / HAS TO / DOESN’T HAVE TO wear a tie at his work. He is a lawyer.
✔ has to
→ Third person singular → "has to".
Also, lawyers often wear ties, so it’s an obligation.

#### 3) You MUSTN’T / MUST smoke in public places. It’s prohibited.
✔ mustn’t
→ Prohibited = not allowed → mustn’t

#### 4) We have a meeting with our boss tomorrow at 9 am. We MUSTN’T / DON’T HAVE TO be late.
✔ mustn’t
→ Being late is not allowed — it's a strict rule.
✘ "don’t have to" implies it’s optional, but missing the meeting is bad.

#### 5) I HAVE TO / MUST / DON’T HAVE TO tidy my room today because I cleaned it yesterday.
✔ don’t have to
→ No obligation since it was already done.

#### 6) We MUSTN’T / DON’T HAVE TO forget to set the alarms before we leave our house.
✔ mustn’t
→ This is a prohibition against forgetting — it's important to remember.
“Mustn’t forget” = you are not allowed to forget.
(“Don’t have to” would mean “it’s not necessary”, which is wrong.)

#### 7) We MUST / DON’T HAVE TO bring our passports or we won’t board the plane.
✔ must
→ It's a requirement — without passport, you can’t fly.
“Must” is stronger and more appropriate than “have to” here (though both could work, “must” is better).

#### 8) You MUSTN’T / DON’T HAVE TO / HAVE TO drink and drive.
✔ mustn’t
→ Drinking and driving is illegal and prohibited.

#### 9) Sarah comes to the party because she DOESN’T HAVE TO / HAS TO / HAVE TO work tomorrow.
✔ doesn’t have to
→ She’s free because she doesn’t need to work tomorrow.
So she can come to the party.

---

✔ B Answers:

1. doesn’t have to
2. has to
3. mustn’t
4. mustn’t
5. don’t have to
6. mustn’t
7. must
8. mustn’t
9. doesn’t have to

---

C. Look at these jobs. Write sentences using MUST, HAVE TO, DON’T/DOESN’T HAVE TO and MUSTN’T. There is only one correct answer for each.

We need to choose the correct modal based on whether something is:
- Required (must / have to)
- Not required (don’t have to)
- Forbidden (mustn’t)

---

#### 1. A waiter
| Task | Sentence |
|------|---------|
| steal food | ✔ mustn’t steal food. (It's illegal and unethical) |
| be nice to customers | ✔ has to be nice to customers. (Professional duty) |
| use a computer | ✔ doesn’t have to use a computer. (Not always required, depends on restaurant) |

> Note: "Must" vs "have to" – both can be used for obligation, but “have to” is more common in everyday speech. For consistency, we'll use “has to” for third person.

---

#### 2. A doctor
| Task | Sentence |
|------|---------|
| understand the human body | ✔ must understand the human body. (Essential knowledge) |
| speak at least three languages | ✔ doesn’t have to speak at least three languages. (Not required for all doctors) |
| be afraid of blood | ✔ mustn’t be afraid of blood. (If they are, they can’t do their job well) |

---

#### 3. A pilot
| Task | Sentence |
|------|---------|
| wear a uniform | ✔ has to wear a uniform. (Standard requirement) |
| be afraid of flying | ✔ mustn’t be afraid of flying. (Would prevent them from flying safely) |
| carry a gun | ✔ doesn’t have to carry a gun. (Not required unless it’s a military or special flight) |

---

✔ C Answers:

#### 1. A waiter
- mustn’t steal food
- has to be nice to customers
- doesn’t have to use a computer

#### 2. A doctor
- must understand the human body
- doesn’t have to speak at least three languages
- mustn’t be afraid of blood

#### 3. A pilot
- has to wear a uniform
- mustn’t be afraid of flying
- doesn’t have to carry a gun

---

✔ Final Summary:

#### A.
1. don’t have to
2. mustn’t
3. mustn’t
4. don’t have to
5. don’t have to
6. mustn’t

#### B.
1. doesn’t have to
2. has to
3. mustn’t
4. mustn’t
5. don’t have to
6. mustn’t
7. must
8. mustn’t
9. doesn’t have to

#### C.
1. A waiter:
- mustn’t steal food
- has to be nice to customers
- doesn’t have to use a computer

2. A doctor:
- must understand the human body
- doesn’t have to speak at least three languages
- mustn’t be afraid of blood

3. A pilot:
- has to wear a uniform
- mustn’t be afraid of flying
- doesn’t have to carry a gun

---

Let me know if you'd like this printed out or formatted differently!