Angularjs : how to write options code for quiz pallet?

In the process of making a quiz website,I have prepared a Question pallet of 25.In that,if i select option 1 on a question and moving to another it seems to be option 1 for rest of the questions.I used radio buttons for the options but i cant figure it out how to prepare answers for individual questions.I used angular js for this and bootstrap also.

This is the code : http://ift.tt/2wS9a7W