An alphabet letter series is given with one term missing: EFGHI, LMNO, RST, WX, ?. Which single English alphabet letter should replace the question mark so that the pattern continues correctly, taking into account wrap around from Z back to A?

Introduction / Context:
This question tests the ability to recognise patterns in alphabet series, a very common topic in aptitude and competitive examinations. The series given is EFGHI, LMNO, RST, WX, ?, and we have to identify which single letter should appear next so that the sequence follows a consistent logical pattern. Understanding how letters progress in the English alphabet and how group sizes and position jumps behave is the key to solving this problem accurately.

Given Data / Assumptions:

• Given series: EFGHI, LMNO, RST, WX, ?
• Each group consists of consecutive English letters.
• The number of letters in each group decreases by one as we move along the series.
• We may need to consider wrap around from Z back to A.
• Answer choices are single letters: A, D, B, E.

Concept / Approach:
The approach is to examine both the length of each group and the starting letter of each group. We look for a regular change in group size (how many letters are in each block) and a regular change in the alphabet positions of starting letters. Once these patterns are identified, we extend them to find the missing term. If letter positions cross beyond Z, we wrap back to the start of the alphabet at A and continue counting in a circular manner.

Step-by-Step Solution:
Step 1: Count the number of letters in each term. EFGHI has 5 letters, LMNO has 4 letters, RST has 3 letters, and WX has 2 letters.Step 2: Notice that the number of letters is decreasing by one each time: 5, 4, 3, 2. Therefore, the next term should contain exactly 1 letter.Step 3: Look at the starting letters of each group: E (5), L (12), R (18), W (23) in terms of alphabet positions.Step 4: The difference between the starting positions is +7 (E to L), +6 (L to R), and +5 (R to W). We see a decreasing pattern of +7, +6, +5.Step 5: Continuing this pattern, the next jump should be +4. So from W (23), add 4 to get 27. Since the alphabet has 26 letters, position 27 wraps around to position 1, which corresponds to the letter A.Step 6: Combine both observations. The next group must be a single letter, and the next starting letter after applying the pattern is A. Therefore, the missing term is A.

Verification / Alternative check:
We can verify by rewriting the starting positions with wrap around in mind: 5, 12, 18, 23, and then 27 becomes 1. The difference pattern 7, 6, 5, 4 is consistent. The lengths 5, 4, 3, 2, 1 also form a clear descending sequence. Both independent checks confirm that A is the unique correct continuation of the given series.

Why Other Options Are Wrong:
Option B (D) does not match the required starting position obtained by applying the decreasing jump pattern. Option C (B) and option D (E) also fail the rule of adding 4 to the previous starting letter with wrap around from Z to A, so they do not maintain the consistent structure of the series.

Common Pitfalls:
Many learners focus only on the visible letters and try to guess the pattern without checking both group size and letter positions. Another common mistake is to ignore wrap around at the end of the alphabet, which leads to choosing letters like D or E merely because they look close to previous terms. Always convert letters to their numerical positions and apply the pattern carefully.

Final Answer:
The correct missing term in the series is A.