Dear Devika, you haven't mentioned your Category. Neverthless, for being eligible for NEET, you should score a minimum aggregate of 50% in Physics, Chemistry and Biology. It is 50% for General Category, 45% for PWD and 40% for OBC,SC,ST. Now if you belong to OBC/SC/ST, you needn't appear for Imrovement exams. But if you belong to General Category, if you have the feasibility of appearing for the exam in only one subject, you can appear and improve your score and then be eligible for NEET.