This is very tricky so I might go wrong here but:
We can go with either x or y here. When we take a quick look at the different statements we see that y is represented in every single one of them so this should be easier.
3x/y=(ANY GIVEN PRIME > 2)
y=3x/(ANY GIVEN PRIME > 2)
I. x=y
You can easily solve for y to equal x (ANY GIVEN PRIME > 2) must equal 3, however things don't end there. It can just as easily be 5,11,17 and it will solve for 3x/y=(ANY GIVEN PRIME). In short X=Y does solve for 3x/y=(ANY GIVEN PRIME > 2), however it doesn't cover everything so it doesn't NEED to be true. //doesn't need to be true
II. y=1
Only by looking at y=3x/(ANY GIVEN PRIME > 2) and not having any restrictions for x and y you can conclude that it's solvable for any y not just 1 //doesn't need to be true
III. As II you can conclude it's solvable for any y not just primes. //doesn't need to be true
So in my opinion it should be A.
However it took me more than 2 minutes to solve(If it's a correct solution of course) so if anyone knows some tips or tricks we can use here please share them.