Hi,
The Present Perfect tense is used when the result of an past action is seen (is important) at the present. This can be found in all textbooks. So, let's consider the following situation: a teacher asked a question to students and one of them didn't hear it. Some time later the teacher asks the student to answer the question.
And now here's my question: Should the student say: "I''m sorry, I didn't hear the question." or maybe "I'm sorry, I haven't heard the question" (the fact that he didn't hear the question has a great importance now, the result is that he can't answer it now).
I'm sorry if my question is unclear.

Thanks a lot for your help.
Pawel