The right letters for question marks (?) in the following series are :

The right letters for question marks (?) in the following series are : A C B E C G D ? ?

M N
L E
G H
I E
This question was previously asked in
UPSC CAPF – 2014
The series A C B E C G D follows a pattern where letters alternate between two sequences. The next two letters are I and E.
The series is A C B E C G D ? ?
Observe the letters at odd positions (1st, 3rd, 5th, 7th, 9th): A, B, C, D, ?
This is a simple alphabetical sequence starting from A (1st letter of the alphabet), incrementing by one letter each time. The 9th letter in the overall series is at the 5th odd position, so it should be the 5th letter of the alphabet, which is E.

Observe the letters at even positions (2nd, 4th, 6th, 8th): C, E, G, ?
This is a sequence starting from C (3rd letter), incrementing by two letters each time (C+2=E, E+2=G). The 8th letter in the overall series is at the 4th even position. The sequence is C(3), E(5), G(7), I(9). The 4th letter in this sequence is I.

Combining these, the 8th letter is I and the 9th letter is E. The series continues as A C B E C G D I E.

Letter series questions often hide multiple patterns within a single sequence. It is useful to examine positions, differences between consecutive letters, or alternating subsequences. Converting letters to their numerical position in the alphabet can help identify arithmetic patterns.