Which answer is correct?!

[BlackCitadel]

Hello,
I have been confused about the answer for this sentence:

The teacher wasn't here,the student was absent.
(Join using: During)
- The teacher wasn't here during the student's absence.
Or
- The teacher wasn't here during the student absence.

Should we add comma and s like this ('s) after the subject "student"?

Thanks for your support!

[Josef]

The teacher wasn't here during the student's absence.