Question

Choose a prime number.

• A. 15
• B. 21
• C. 23

Answer 1

The correct option is C 23

$15=5\times 3=1\times 1521=7\times 3=1\times 2123=23\times 1$

$23$ does not have any other factor except 1 and itself.
Hence, $23$ is a prime number.