Dear Tamanna, you can choose upto 3 exam centres. The choices need to be filled in the order of preference. Say for example out of Delhi, Mumbai and Kolkatta, you prefer Delhi then Kolkatta and at last Mumbai, your selection should be in the order of Delhi, Kolkatta and Mumbai. Once the form is submitted, you cannot make any changes. The final selection of exam centre lies with NTA who is the exam conducting authority.