A prime number must be?

• A. Divisible by itself and any other number
• B. Divisible by itself and 1 only
• C. Even
• D. Less than 10

Answer: (B)

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 it can only be divided evenly (without leaving a remainder) by the number 1 and the number itself. For example, the number 5 is prime because it can only be evenly divided by 1 and 5.

The other options do not accurately describe prime numbers. For instance, not all prime numbers are even; actually, 2 is the only even prime number. Additionally, prime numbers can certainly be greater than 10 (such as 11, 13, and higher). Therefore, the defining characteristic that makes option B correct is that prime numbers are specifically defined by their divisibility by themselves and 1 only.