Quiz | How to record first selected option as final answer by user.

I am creating a standard quiz using Adobe Captivate 9. The thing I want to achieve is that when user takes the quiz, I want the first selected option of user to be recorded as his final answer to that question irrespective of what the actual answer is.

For example, I create question -

What is sum of 5 and 2?

A.  6

B. 8

C. 7

D. 10

User sees the above questions and selects radio button A. (which is 6). Though the answer is 7, he changes his answer to option C. (which is 7).  as soon as he clicks on C option, the following message comes up " correct". After this, user clicks on next button.

Captivate should use the first selected option of each question to tabulate the final score.