The relevant question for that is “What might be on the exam?”.
[EDITED to add: But, sure, it might be reasonable for the person teaching the course to say “by the way, this specific thing will be on the exam” for that purpose. What’s much worse is if students are aware of a substantial quantity of the course that is stuff it’s supposed to be teacing them as opposed to incidental fluff, but that definitely won’t be being examined.]
The relevant question for that is “What might be on the exam?”.
[EDITED to add: But, sure, it might be reasonable for the person teaching the course to say “by the way, this specific thing will be on the exam” for that purpose. What’s much worse is if students are aware of a substantial quantity of the course that is stuff it’s supposed to be teacing them as opposed to incidental fluff, but that definitely won’t be being examined.]