RAS question
Find the missing letter in the series: A, C, E, G, ?
Correct answer: (B) I.
The missing letter in the series A, C, E, G is I because the sequence advances by two alphabet positions each time.
Explanation
The series uses alternate letters of the English alphabet. A is the 1st letter, C is the 3rd, E is the 5th, and G is the 7th, so the next term must be the 9th letter, I. The key is to look at the positional gap rather than the sound or shape of the letters: each step skips exactly one intervening letter. NCERT frames this kind of work as part of learning to look for regularities and patterns, use logical reasoning, and verify conjectures obtained from patterns. Here, the observed regularity is a constant difference of two positions, which confirms option B.
Why the other options are wrong
- (A) H follows G immediately, but the established pattern skips one letter after every term, so H must be skipped.
- (C) J is three positions after G, whereas the series keeps a constant gap of two positions.
- (D) K is four positions after G and would break the alternate-letter pattern shown by A, C, E and G.
Concept
This tests alphabet-series pattern recognition under Reasoning & Mental Ability. It recurs in RAS-style reasoning because such questions check whether the candidate can identify a positional regularity quickly and apply it consistently.