Which of the following must be true

Which of the following must be true? 1) Every prime number greater than 5 can be written as either as 5n+1 or 5n-1 2) Every prime number greater than 5 can be written as 4n+1 or 4n-1 3) Every number greater than 5 of the form 5n+1 or 5n-1 is a prime number.

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #29682