Prime numbers are not divisible by any number but themselves or 1.
A) 115 is divisible by 5, so it is not prime
B) 273 is divisible by 3 (you get 91), so it is not prime
C) 317 is prime! only divisible by itself or 1
D) 414 is divisible by 2, so it is not prime. Even numbers are never prime because they are divisible by 2!
