Obligation, possibility, probability explained in English Lesson 47

Lesson 47


1/Sentence Practice

I must be at the hospital at nine thirty in the morning and I mustn’t eat beforehand.

You have to give a blood sample and you haven’t anything to worry about.

I need to be awake early but I needn’t wake too early or I will be starving hungry.

I don’t have to punish myself unnecessarily.

I forgot to tell you, I had to buy you some new pajamas yesterday.

You didn’t have to, the old ones weren’t so bad.

You don’t need to worry they were really good value.

You mustn’t take any metal objects with you. It will stop the scan working properly.

Anyway, I am coming with you. You don’t have to do that. The phone is ringing it must be my mother.

It can’t be her. I tried to phone her ten minutes ago and I couldn’t get an answer. She must be trying to return your call.

You ought to answer it. That’s funny it was about the dishwasher.

I couldn’t really understand the accent, I think the person might be Polish or she may be Hungarian.

There are so many different accents in London.

I phoned your mother and there was no answer. She must be outI should phone her tonight without fail.


2/Vocabulary Practice

  • Obligation
  • possibility
  • probability
  • to be at
  • I mustn’t eat beforehand.
  • You have to
  • a blood sample
  • anything to worry about.
  • I need to be
  • awake early
  • I needn’t wake too early
  • to be starving hungry.
  • to have to punish oneself
  • unnecessarily
  • to have to buy
  • some new pajamas
  • You didn’t have to
  • the old ones
  • so bad.
  • really good value.
  • You mustn’t
  • metal objects
  •  to work properly.
  • You don’t have to do that.
  • the phone is ringing
  • it must be my mother.
  • It can’t be
  • to get an answer
  • She must be
  • to return your call.
  • to answer
  • to be about
  • the dishwasher
  • the accent,
  • might be Polish
  • maybe Hungarian.
  • accents
  • She must be out
  • without fail


Obligation, possibility, probability.

Obligation, need, possibility and probability

  1. Obligation

The modal verb “Must” is used for an instruction or a command.

  In the park dogs must be kept on a lead.

  Lights must be out by 8pm.

  Music must be kept down after 10pm.

  Cars must not be parked in front of the emergency exit.

“Have” and “have got” mean that circumstances oblige someone to do something. We sometimes find that the two meanings overlap.

The school is obliged to give a refund if the class is cancelled.

The muggers forced her to reveal her credit card’s pin number.

I had no alternative/choice but to sell my car; I owed the bank £20,000.

Was music class obligatory / compulsory at your high school? No, it was optional at ours.

They will be liable to pay tax if they work.

He is exempt from tax as he is a student. (exempt = free from obligation)

The negative forms of “must” and “have to” or “have got to” are formed with “need” and “have to”, when they mean something is not necessary / not obligatory.

He can hire a bike, but he has to pay a £70 deposit.

She doesn’t have to buy health insurance, it is optional.

They will have to sell the house, I’m afraid they have no choice/alternative.

She is losing 500K a year, so the company is obliged / forced to close down/ has to close down.

He is over 50, he is exempt from military service/ not obliged to do military service.

  1. Scales of probability: “won’t happen / can’t happen” to “will happen / has to happen”:







Most of the elderly are in need of more company and social interaction; they are often very lonely.

A dog living to 40 is absolutely impossible.

Snow on these slopes within the next four days is highly likely.

Failing this exam is quite possible due to the low pass rates and the exam’s randomness.

Failure is inevitable with such a negative mindset.

A majority of people suffer from a lack of time or of money.

A fourth divorce for him? Very possible if they continue to argue like that.

Filling out a tax return is obligatory once a year in most of these countries.


More vocabulary:

to be liable = to be obliged to pay

to be obliged = it is a must, you have to do it by law

to force = to oblige someone to do something even through they do not want to

to have no choice by = to have no alternative but = to have no other way than

mandatory = automatic, there is no alternative

compulsory = obligatory

optional = you can choose

exempt = free from obligation

in need of = need / want (more formal)

need for = we feel a need for

shortage = there are not enough

through lack of = to have none or not enough

an absolute necessity = something you must have

do without = survive or live without

requirements = things you must do or need

an opportunity = a real chance

inevitable = certain de happen

it is doubtful whether = it may not improve

it is probable that = it could be, there is a possibility

certainty = will certainly happen

Questions and Answers

Questions and Answers

What time do you have to be at the hospital?

I must be at the hospital at 9:30 in the morning.

Do you have to give a blood sample?

Yes, I have to give a blood sample.

Did you understand that man?

No, I couldn’t really understand the accent.

Do you think you ought to answer him?

I think I ought to  answer him, yes.

Do you really need to make all the noise?

Yes, I’m afraid I have to.

What should you say?

I should say that I am sorry.

When must you go?

I must go before the end of the month.

Can it be her?

No, it can’t be her.

Must you take it so seriously?

Yes, I must, my job depends on it.

Might you be Polish or Hungarian?

Yes I might, I am Polish actually.

Exercises Lesson 47

Comprehension Practice

Vocabulary Practice

Grammar Practice

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