x is a positive integer. I. Given : x is a prime number. GCD (2, 300) = 2 (prime) GCD (Any prime no. other than 2, 300) = 1 (Non - Prime) ⇒ GCD may or may not be prime. ∴ I alone is not sufficient. II. Given x > 5 GCD (6, 300) = 6 (Non - prime) GCD (22,300) = 2 (Prime). ∴ II alone not sufficient. I & II. x is a prime number greater than 5. GCD (A prime no. greater than 5,300) = 1 (Non-prime) ∴ I & II together are sufficient.