Number of letters skipped in between the adjacent letters in the series are consecutive even numbers.
Which of the following series observes this rule ?

Answer: B. ADIPY
A B  C D E  F  G  H I J  K  L  M  N  Q P Q  R  S  T  U  V  W  X Y
  2   4   6   8  

2, 4, 6, 8 are consecutive even numbers.