Dear Aspirant,

Yes, biology as an additional subject is eligible for giving NEET Exam.

you must have passed in English and in both the theory and practical  of PCB i.e Physics, Chemistry and Biology with at least  50  % in aggregate of PCB in 12th examination  if belong to general category , or   at least  40%  in aggregate of PCB if belongs to  Obc/ Sc /st.

For more details-

NEET Eligibility Criteria 2021 - Qualification, Age Limit, Marks Required (careers360.com)

Hope it Heps!