Hey Viraj.

As per the eligibility criteria laid out for NDA you need to pass class 12th board exams from any stream to be eligible to join the Army wing. So being a Biology student, you are eligible to join the Army wing through NDA. But to be eligible to join the Naval or the Air force wing you must have passed Class 12th board exams with Physics and Maths as subjects. Hence if you did not study both these subejcts in 12th you will not be eligible to join the Naval and Air force wing. But you are eligible for the Army wing.

Best of luck