Explanation:

- "In the university": This phrase implies being inside the university physically. It's not the most common way to express attending for studies.

- "At the university": This is the correct and most common form. It indicates being enrolled or studying academically at the university.

- "On the university": This would imply being on top of the university or physically on its premises, not appropriate for context.

- "From the university": Typically used to indicate origin or point of reference, like graduating from.