There are 6! permutations of the 6 letters so you know that has to be your denominator.

If you join the two letters they can be in seats 1&2, 2&3, 3&4, 4&5, or 5&6.

So there are 5 seat combinations that they can occupy and they can go QP or PQ so I believe the answer is 5!*2! / 6!.

Answer A.