Grammar for ielts fiona Aish & Jo Tomlinson ■L& 11

Modal verbs for deduction in the past:
Must/m ustn’t 
is used 
from the speaker's point of view to express a strong likelihood in the past
m u st/m ustn't + have +
past participle 
OR 
m ust/m ustn't + have + been +
past participle
The prim e m in iste r m u stn 't have kept his promise about increasing alternative energy form s, 
as I've seen nothing in the news about it. 
(I think 
it was likely he didn’t keep his promise)
Note: M ustn't 
can be replaced by 
couldn’t 
fo r the same meaning.
Might/may/could 
is used 
to express possibility in the past
m ight/m ay/could + have +
past participle (Also 
m ight/m ay/could + have 
+ 
been 
+ verb(-/7ig))
A curb on the use of fossil fuels m ight have curtailed the pollution problem , (it was possible)
Note: 
Modal verbs of deduction 
[m ust/could/m ight/m ay +be) 
can also be used in the present, but it 
is unlikely that you w ill see this in an IELTS exam.
Modal verbs for past ability:
Could 
is used:
1 
To express ability
I could swim 100 metres, but I can’t now.
2 
To say that something was allowed
People could travel w ithout a passport 200 years ago. (it was allowed)
Could not (couldn't) 
is used:
1 
To express inability
I couldn’t com plete my essay on global w arm ing.
2 
To say that something was not allowed
He couldn't go into the monkey enclosure, (it was not allowed)
Grammar for IELTS
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