in the series D is coming after B , there is 1 letter skipped between . H is coming after D, there are 3 letters skipped in between .
Hence N must come after H which is having 5 letters gap in between . This is first logic based on which N is the answer .
Second Logic :
B's position is 2 , D's position is 4 and H's position is 8. Hence logic is letters are presented in geometric multiples of 2 . Hence 16th position letter must come after H which is P .
Reference .
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26