In this type of questions, you are given alphabets from A to Z. The position of a letter is given in the form of a puzzle. The candidate is required to find yhis letter. However, sometimes a random letter series is given and the candidate is required to find out how many times a letter satisfying the conditions specified in the question, occurs.

H  D  Y  S  M  W  N  B  Q  P  O  C  R  T  B  L  Z  V  E  G  U  F

Which is the only letter that occurs twice ?

A. B
B. E
C. M
D. S
Answer: A . B


Clearly, B occurs twice.