Which sentence is grammatically correct (or maybe both) and why?
- I have been studying for my exam since lunchtime and now I am watching TV. or
- I had been studying for my exam since lunchtime and now I am watching TV.
The situation is as follows (it's from a student's book):
- Is that the TV I can hear?
- Yes, Dad. I (to study) for my exam since lunchtime, and now I (to watch) TV.
I believe the Present Perfect Continuous has to be used here since I haven't passed the exam and taking a break now. On the other hand, there is no visible result of my activity, as in "I'm exhausted. I've been studying for an exam", and the speaker has stopped/finished studying.
Thank you in advance.