certainty and possibility; ability
CONTEXT LISTENING
Look at these photos of two ordinary objects. What are they?
You are going to hear part of a quiz programme. Were you correct?
Listen again and complete these sentences.
Grammar
Certainty and possibility
Must
When we’re sure something is true, we use must:
It must be a pen because that looks like ink.
They must be at home because the light is on.
Might, could, may
When we think something is possible, we use might/could/may
It could be a butterfly because those are its wings.
He might be her brother but I’m not sure.
Can’t
When we’re sure something isn’t true, we use can’t:
It can’t be a butterfly because it hasn’t got a body. (not It mustn’t be a butterfly.)
That can’t be Sue’s car because hers is at the garage.
Note:
We also use might/could/may when we are uncertain about the future:
I may go to Greece next month. (= it’s possible but I’m not certain)
My football team might win the cup.
Ability: I can ..., I’m able to ..., I could ...
I can
I can = I know how to do something or it is possible for me to do something.
+ The children can swim but they can’t dive yet.
+ I can help you on Monday but not on Tuesday.
– I can’t decide what it is.
? Can you say what’s in your photo?
Be able to
In the present we use can (a modal verb) or be able to (not a modal verb).
My grandfather is able to cook his own meals but he isn’t able to walk to the shops.
I’m not able to answer that question.
Note: Be able to is less common
Past ability
In the past we use could or was able to:
He could / was able to walk when he was one.
The athletes couldn’t/weren’t able to train because the weather was bad.
Other tenses
For all other forms, we use be able to:
Future: Team A will be able to come back next week.
Present perfect: Team A hasn’t been able to answer the question yet.
Infinitive: Team A hopes to be able to come back next week.
Other uses
We also use can and could for permission, offers and requests. See lesson Modals 1
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