Few options here:
1. Core Data
Prepopulate .sqlite file with questions and include with app. Keep track of user's progress and attempts and whatever other stats.
This approach also give your ability to label questions by a topic (or any other criteria) and present questions to user that they need or that they failed most.
2 Get data from server
A bit more complicated but offers more benefits. With this approach you would be getting questions in json format.
Benefit of this approach is that you can add any number number of questions and tests without resubmitting your app.
3. Store as text/plist with app
Yes, you can also store your questions as text in plist or json format and as app loads populate core data or keep it in memory to display. The latter approach, however, would offer the least amount of benefit and flexibility to the user.