wasn't listening vs didn't hear

[Inez]

Dear teachers

I think the answer that was given to the question below is not correct. The answer should be written as (a) wasn't listening. Si?

I'm terribly sorry but I ......... what you said just now and I wonder if you could repeat it.

(a) wasn't listen to
(b) wasn't hearing
(c) didn't hear
(d) didn't hearing

[Kitosdad]

Inez, the answer is " didn't hear".

It is obvious that you weren't listening if you didn't hear. OK?
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