You can replace some names in order to identify the correct pronoun. For instance:
- Les professeurs (ils)
I’ve already helped you with this one in the text 🙂
What about the rest of the examples?
We have for instance , les cours.
You can think of les cours as ils (they).
The next example is easier to replace: Certains élèves – ils (they).
I think you are able to replace the other examples on your own. You can always leave me a comment if you need help.