Explanation : This series is formed by moving +2 and +3
for each pair of letters starting from left. Thus, the
missing letter is N + 3 = Q. Alternative solution: Skip one and two letters
alternately to get the next letter, i.e., skip two letters O
and P after N to get Q.
Explanation : B = 2, ... K = 11 according to the alphabet
series. Thus, the alphabet series have been
constructed according to the prime numbers. The next
prime number is 13 and the corresponding letter is M.