Thank you very much for explaining to me the best choice.

I still have a few sentences I'm doubtful of. I included 7 doubts using question words. Thank you

1) Sometimes my parents aren't at home for (?) their work and so I have to stay at home alone with my brother.
2) I felt sorry for my mum because she has a broken leg (better: she broke her leg, she had a broken leg).
3) I finished primary school with an average mark of 9 out of (?) 10.
4) I was proud of myself on 24th July when I passed my driving test.
5) The teacher reprimanded me (= wrote a reprimand in the class register??)
6) It was the last sad moment in my life when my girlfriend broke up with me (?). While I was climbing a step I fell on the floor (?)(I fell down on the floor)

1 answer

1) Sometimes my parents are at work, not at home, so I have to stay at home alone with my brother.
??

2) I felt sorry for my mum because she has a broken leg (better: she broke her leg, she had a broken leg).
I'd say "... because she broke her leg."

3) I finished primary school with an average mark of 9 out of 10.
OK

4) I was proud of myself on 24th July when I passed my driving test.
OK

5) The teacher reprimanded me (= wrote a reprimand in the class register??)
OK, either way you want to write it is fine.

6) It was the last sad moment in my life when my girlfriend broke up with me. While I was climbing a step, I fell down.
If you fall down, "on the floor" is usually assumed -- or "on the field" if you're outdoors, etc.
I don't understand "last sad moment" -- do you mean this? ~~> The last time I felt sad was when my girlfriend broke up with me.