1. Who are they?
They are student reporters.
2. What are they?
They are student reporters.
3. What's their job?
They are student reporters.
4. What do they do?
They are student reporters.
(Which questions are suitable for the answer?)
The answers in 1 and 2 are fine.
For 3 and 4, I'd answer this: They are to report the news about campus activities, including sports.