'Have not been able' or 'could not'


Senior Member
'Have not been able' or 'could not': which one should I use in the following sentence?

'Sorry sir, I have been busy for the last few days so I could not do/ have not been able to do my homework.'
  • PaulQ

    English - England
    have not been able to do is better. It is a little more formal and it indicates more clearly that there was an exterior reason that prevented you.


    English - England
    I did not suggest that: "could not" is possible, but I do not think that it is as good.


    Senior Member
    British English (Sussex)
    If the time reference is more specific we tend to prefer the simple past:

    If the student was given his homework the day before:
    Student: Sorry Sir, but I had a terrible stomach-ache last night...so I couldn't do my homework.
    Teacher: Why didn't you get up early this morning to do it then?

    Since the OP context is the student's having been busy for "the past few days", the present perfect covers the whole period, right up to the present.

    Either would be correct for your sentence though, as PaulQ notes.
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