In this type of questions, a series of single, pairs or groups of letters or combinations of letters and numerals are given. The terms of the series form a certain pattern as regards the position of the letter in the English alphabet. Find the missing or wrong term in series 

1)

R, U, X,A, D, ?


A) G

B) F

C) H

D) I

Answer:

Option A

Explanation:

$R + 3  \rightarrow U, U + 3 \rightarrow X, X + 3 \rightarrow A, A + 3\rightarrow D, D + 3\rightarrow G$

Hence the answer is (a).