Present perfect tense

We use the past simple for completed actions, where a past time reference is indicated. The past simple always refers to a past action.

With the present perfect tense, a clear time reference is very often not stated. The present perfect may or may not refer to a past action

Note:
Sometimes we use present perfect for an action that occurs during a period of time that is not yet finished. A clear time reference is given here but the action is not yet over. Let us illustrate this with some examples:

· We have simplified the application procedures this year. (It is still this year.)
· I have been inundated with e-mails today. (It is still today.)
· We have seen dramatic developments in the internet over the past decade. (It includes now/up to now.)

What is the difference between:

a) Have you been busy this morning?
b) Were you busy this morning?

In a) it is still this morning (before 12 noon), whereas in b) it is clearly the afternoon, evening, or later in the day.