Thanks for the question! So this is a strengthen with sufficient premise question. First of all, what’s the conclusion? Well, it’s that the athletes receive fair salaries. Now how can we get there?
(E) tells us that if a professional athlete’s salary is fair, then it’s determined by what an individual’s WTP for the athlete’s services in an unrestricted free market. This one we can actually eliminate pretty quickly, because we diagram it as
Fair salary —> WTP
But we want something to conclude in fair salary, in other words
X —> Fair salary
And we can’t get that from (E), since fair salary is in the sufficient, but we want it in the necessary. That’s a mistaken reversal.
(D), on the other hand, tells us that any salary that a team owner is willing to pay for the services of a professional athlete is a fair salary. That’s diagrammed
WTP —> Fair salary
And that’s what we want! (D) has it the correct way, and so is the right answer.
Hope this helps! Feel free to ask any other questions that you might have.