In this type of questions, two groups of alphabets related to each other in same way, are given. The candidate is required to find out this relatonship and choose a group of alphabets which is related in the same way to a third group provided in the question.
ABCD : OPQR : WXYZ : ?
Clearly, each letter of the first group is moved fourteen steps forward to obtain the corresponding letter of the second group.
A similar relationship will exist between the third and fourth groups.
Hence, the answer is (b).