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)

Z, X, S, I, R, R, ?, ?


A) G, I

B) J, I

C) J, K

D) K, M

Answer:

Option A

Explanation:

$Z-2 \rightarrow X, X-5 \rightarrow S, S-10 \rightarrow I, I-17 \rightarrow R,$

$R-26 \rightarrow R, R-37 \rightarrow G, G-50\rightarrow I$

Note that the numbers representing the difference between the consecutive terms of the series again forms a series -2,5,10,17,26,37,50- in which the pattern is +3, +5, +7, +9, +11, +13.