Dear Mahima,

Yes, the official answer key will be changed if the challenged question in the key has the wrong answer. However, you have to pay a sum of Rs.1000 as online payment in the official website to challenge. Your amount will be refunded if the challenge is found to be correct. The chances depend on your accuracy level. If you are very sure with the answer and discussed with your friends and teachers, you can surely challenge and the answer will get changed. Last year also, an answer was change after challenging.