Ответ:
Here are the completed sentences based on the text:
- School in America begins a) at the beginning of September
- Jason doesn't like it when a) summer holidays finish
- Jason lives in b) a big American city
- On the first days of school pupils a) talk a lot
- Jason's classes begin at 9 a.m. c) on the first day of school
- Jason thinks the first days of school after holidays are c) his happiest days at school
