The wording of this question is awkward. I'm not sure what it's looking for:
"Eventually, globally, 'z' holds is necessary for 'n' holds"
And then, based on the commas, I guess the answer should have the form "F(G(_))" for some _ that says z is necessary for n. But none of the options have that shape!
The correct answer is (F (n -> (G z))) ... and I'm not sure how to describe this cleanly in English.