Put in a/an or the in these sentences where necessary1. Would

Put in a/an or the in these sentences where necessary
1. Would you like apple?
2. How often do you go to dentist?
3. Could you close door, please?
4. I'm sorry. I didn't mean to do that. It was mistake
5. Excuse me, where is bus station, please?
6. I've got problem. Can you help me?
7. I'm just going to post office. I won't be long
8. There were no chairs, so we had to sit on floor.
9. Have you finished with book I lent you?
10. My sister has just got job in bank in Manchester.
11. We live in small flat near city centre.
12. There's small supermarket at end of street I live in