Hey Bhuwan.

Yes, a Biology student can apply for NDA. You will be eligible for the Army wing of NDA.

As per the eligibility criteria of NDA, you need to pass Class 12th board exams with any subjects/ stream to be eligible for the Army wing. But to be eligible for the Naval/ Air Force wing you must have passed Class 12th with Mathematics and Physics as a subject. Hence you are eligible for NDA for the Army wing but not for the Navy/ Air Force wing.

Best of luck