Rob and Stephen look at how ‘must’, ‘could’ and ‘perhaps’ can be used to speak about certainty and possibility.

Watch the video. Then go to the Tasks and do the activities.


Language level

Intermediate: B1


Hi guys ,
In Task (3) number (6) they said (could have just left ) , is there any difference if i say ( might be left ) both are predictions .
Many Thanks .

Hi Fouka,

These are examples of modal verbs used for deductions about the past. There are five alternatives:

must have + past participle (a very strong, almost certain decuction)

may/might/could have + past participle (a less strong, possible deduction)

can't have + past participle (a very strong, almost certain negative deduction)

As you can see, we can use 'could', 'may' and 'might' interchangeably, so the answer to your question is that both 'could' and 'might' are possible.

Best wishes,



The LearnEnglish Team

i have a problem to solve Task 2 please help me.

Hi Bushra,

The grammar in this exercise is explained on our modals + have and may, might, may have and might have pages - take a look at those and then try the exercise again. If that doesn't help, please explain to us what parts you don't understand and we'll be happy to help you.

Best wishes,
The LearnEnglish Team

i must confess this has been a good way to learn this kind of common expression to use in our life. although at the beginning was hard to understand and used them quickly, just take me a few minutes to understand it and put it into practice.
must have been a murderer
could have been tea

Hello Learn English team
How can I write an essay for the IELTS exam?
another question
what is the difference between using present continuous and the formula "be going to + inf " for the future

Hi ahmed only,

I'd suggest you explore our IELTS section and TakeIELTS for advice on how to prepare for the writing section of the IELTS.

Please see our talking about the future page for an answer to your other question. Please note that you can search for topics using our Search box (on the top right of the page).

Best wishes,
The LearnEnglish Team

Hello Sir,
In question 4 of task 2, we have this sentence
"He must spend a lot of time practicing"

It looks like the speaker is giving advice to Adam. Is he giving advice or just saying what he thinks Adam might be doing?

Does this sentence mean the same as 'He must be spending a lot of time practising'?

Hello Adtyaggrwl,

In question 4 the speaker is not giving advice but is rather making a logical deduction about Adam based on the evidence he has. In other words, he sees that Adam is a good musician and speculates on the reason for this.

The choice of 'spend' or 'be spending' is a choice of simple or continuous forms. You can find more information on when to use continuous forms, and how they differ from simple forms, here.

Best wishes,



The LearnEnglish Team

Thanks for the clarification. But, in a different context, can the sentence 'He must spend a lot of time practising' also mean a suggestion?