Which of the following numbers 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. This means that a prime number can only be divided evenly (without a remainder) by 1 and the number itself.

In the provided options, 7 stands out as a prime number because its only divisors are 1 and 7. There are no other numbers that divide 7 evenly.

In contrast, the other numbers listed can be factored into smaller positive integers. For instance, 4 can be divided by 1, 2, and 4; 9 can be divided by 1, 3, and 9; and 8 can be divided by 1, 2, 4, and 8. Since these numbers have divisors other than 1 and themselves, they do not qualify as prime.

Therefore, 7 is confirmed as the only prime number among the options provided.