Gap year and A-levels

My mate got AAB in his A-levels in August 2012.

In his AS year he dropped biology after getting a grade B and continued with the rest of his A-levels.
He now wants to continue with biology a-level which he dropped by completing the A2 exams. the question is: will he be considered as a retake student if he does his A2 exams in his gap year because it will have taken him 3 years to complete the subject or not because he hasnt yet done the A2 exams and therefore hasn't resat the exams.

thanks for reading