Dear Candidate,

It is totally based on which exam you have taken . As you know , various exams conducted by online/offline method , and for objective questions .. OMR sheet is used for offline answering while Online  answering is computer based now-a-days .

Answer key or Response sheet of candidates with correct option ,any of these or both are available for individual competitive/entrance exams , you can consider both as the final answer .

Well, It would be better for me to help you if you tell about which exam you are questioning about .

Hope you understand !

Best wishes !!