Oil prices have gone up again!
I've been trying to solve this issue.
She's been working here for ages.
I've read two good books this year.
I've never tried African food.
I've spoken to him recently.
I've repaired the car.
A continuous activity which started in the past and hasn't finished yet.
General life experience (time not stated)
Unfinished activity
Result of things completed "so far"
Talking about visible change
Showing final effect (task completion)
A completed activity (time not given)