Which number is a prime number?

• A. 4
• B. 9
• C. 11
• D. 12

Answer: (C)

A prime number is defined as a natural number greater than 1 that has no positive divisors other than 1 and itself. This means that a prime number cannot be formed by multiplying two smaller natural numbers.

In the case of the number 11, it meets the criteria for prime numbers because the only divisors of 11 are 1 and 11. There are no integers other than 1 and 11 that can divide 11 without leaving a remainder. Thus, 11 is not divisible by any other whole number, confirming its status as a prime number.

On the other hand, the other numbers presented are not prime. The number 4 can be divided by 1, 2, and 4, making it composite. The number 9 can be divided by 1, 3, and 9, which also categorizes it as composite. Similarly, the number 12 has divisors that include 1, 2, 3, 4, 6, and 12, confirming that it is composite as well. Therefore, 11 stands out as the only prime number in the group.