Which of the following is a prime number?

A prime number is defined as a natural number greater than 1 that has no positive divisors other than 1 and itself. In this case, the number 5 meets that criterion. It can only be divided evenly by 1 and 5, which makes it a prime number.

In contrast, the other numbers provided can be evenly divided by numbers other than 1 and themselves. For example, 4 can be divided by 1, 2, and 4; 6 can be divided by 1, 2, 3, and 6; and 8 can be divided by 1, 2, 4, and 8. Therefore, they do not qualify as prime numbers. This distinction highlights the unique property of 5 as the only prime number among the choices listed.