Question

Which of the following pairs are twin primes?

• A. $(19,21)$
• B. $(29,31)$
• C. $(39,41)$
• D. $(49,51)$

Answer 1

The correct option is B $(29,31)$

Twin primes are prime numbers that differ by$2$.

For example 11 and 13 are twin primes.

In a sense they are “right next to each other” in the sense that(with the exception of the prime number $2)$,

two primes can’t be closer together.

$21$ is not prime though. so $19$ and $21$ are not twin primes.

$19$ and $17$ are twin primes, but the next prime after $19$ is $23$ which is more than $2$ greater.