1. I've been learning the piano for two years.
B. talk generally about situations or activities that started in the past and are still continuing now
2. I've been practicing the piano since 10 AM.
A. emphasise how long an activity has been happening. The activity may or may not be complete.
3. I've been playing the piano all day and I'm tired now.
C. talk about situations or activities that have stopped but have a result in the present