Hello Ajay, I don't understand your situation. How can you pass the class 12th exam because you had earlier completed the board registration through maths, right? Because you told that you failed in class 12th so that means that you registered CBSE through maths. Let's assume that you passed 12th board exam with bio then how were you allowed to write bio in 12th without completing 11th? Its someone's fault. Either yours or your school's. Ask the school to keep your documents ready in case of verification. Talk to MCI exam conductors once and tell them about your problem. I haven't heard about a situation like this before.