Hii..

As you ask about how it is difficult to qualify Christ University BBA entrance exam..

so as you are mentioned that you are in 12 th . So you have enough time to prepare for that exam.. there  is nothing like hard exam ...you can easily qualify that exam by clearing your basics and doing some hard work.. stick to the syllabus of the entrance exam clear your all doubts and go through whole syllabus and revised 2 or 3 time for your entrance exam . This will help you more qualify in exam.

All the best!!