6. Given that $p$, $p+14$, and $p+q$ are all prime numbers, and $p$ has a unique value corresponding to it. Then $q$ can only be ( ).
(A) 40
(B) 44
(C) 74
(D) 86
6. A.
$q$ can only be 40. When $p=3k$, $p$ can only equal 3, which meets the requirement; when $p=3k+1$, $p+14$ is not a prime number; when $p=3k+2$, $p+40$ is not a prime number.