My father CAN PLAY the violin.
ability: present
My mother COULDN'T DRIVE until she was 40.
ability: past
CAN I MAKE a suggestion?
asking for permission
COULD I USE this phone for a moment?
asking for permission: more polite
You CAN HAVE a break now.
giving permission
You CAN'T PARK here.
no permission
CAN YOU GIVE this letter to Fay?
requesting
COULD YOU PASS me the salt, please?
requesting: more polite
I CAN DO the shopping if you like.
offering
COULD I MAKE you a cup of tea?
offering: more polite
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