For this question, I thought the correct answer is A, because if we look at the electrode potential, that of iron(III) is higher than that of iodine, therefore the equilibrium for $\ce{Fe^3+}$ will favor the RHS, and shifts to the right, and therefore iodine will go in the opposite direction. Therefore A would be correct.
But the correct answer is D. Using the same logic, I can see it is also correct, but why isn't A correct then?
Thank you for any ideas in advance and sorry for the trivial question.