The prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.
A.
7 - is a prime number
17 - is a prime number
63 - is not a prime number because 63 = 3 × 21
B.
3 - is a prime number
11 - is a prime number
23 - is a prime number
31 - is a prime number
C.
1 - is not a prime number
D.
2 - is a prime number
3 - is a prime number
5 - is a prime number
15 - is not a prime number because 15 = 3 × 5