Hello Hardik

Science is not compulsory in 12 if you want to prepare for NATA exam. You can take commerce or arts as well. Yes physics, chemistry and Mathematics are compulsory subjects as eligibility criteria says. Applicants must pass class 12 with physics chemistry and mathematics with minimum 50 percent marks from a recognized board. But taking science in plus two will help you a lot and it is always better to have science back ground as this  will help you later in during your course time as you will have subjects like structure ,mechanics etc. which at times can be tough to deal with without a science back ground.

Thankyou

Best wishes for your Future