I think this gives you a good chance to expand your abilities. You can start with 70 multiple choice questions that you read up from a next file, with the answer key in another plain, unencrypted text file.
You can move on to adding questions with textual responses, numeric only responses, etc. to expand your knowledge of the controls provided by IB.
You can then expand to storing the questions/answers in XML as lazydog mentioned, and then you could move on to encrypting the XML for the answer key to learn about that. If you wanted to be really paranoid you could avoid reading up/decrypting the answer key until the user has "submitted" the test. Obviously anything that is unencrypted in memory can be accessed, but if the user has already submitted their test, the answers won't help them anymore.
You could also expand to having the questions XML on a remote server that you pull from, to learn about how to do that, and if you wanted to get really ambitious you could run some sort of web service/CGI thing that takes the user's responses and returns correct/incorrect and their score, keeping the answers safely out of the user's hands.
-Lee