The answer is c. courtroom : lawyer.
The original analogy, football field : head coach, is comparing a workplace to a profession that would work in that workplace. A, B, and D don't fit that description (A is comparing two similar professions, B is comparing a job with a task that person would do, and D is comparing two people) so C is your best option (it, too, follows the format of workplace : profession.)
Hope this helps!