Which of the following is a prime number?

• A. 9
• B. 12
• C. 13
• D. 15

Answer: (C)

A prime number is defined as a natural number greater than 1 that has no positive divisors other than 1 and itself. To determine whether a number is prime, we assess whether it can be divided evenly by any number other than 1 and itself.

In the case of the number 13, it meets the criteria for a prime number. The only divisors of 13 are 1 and 13; thus, it cannot be evenly divided by any other numbers. Since it is not divisible by any other integers, it is confirmed as a prime number.

For the other options, 9 can be divided by 1, 3, and 9. Since it has divisors other than 1 and itself, it is not prime. The number 12 has multiple divisors, including 1, 2, 3, 4, 6, and 12, making it composite. Similarly, 15 can be divided by 1, 3, 5, and 15, also categorizing it as composite. Thus, among the choices given, only 13 satisfies the conditions of being a prime number.