Is $1$ a prime number or a composite number?

The correct option is B $1$ is neither prime nor composite.
A prime number is a whole number with exactly two factors, 1 and the number itself.
For example, $2,3,5,7,$ and $11$ are prime numbers.
Composite numbers, on the other hand, have more than two factors.
For example, $4,6,8,9,$ and $10$ are composite numbers.

$1$ does not fit in either of the two conditions. Hence, $1$ is neither prime nor composite.