A letter series is given with one term missing. Choose the correct letter that will complete the sequence: R, M, I, F, D, ?

Introduction / Context:
This question is a single-letter series that requires recognising how the letters move backward in the alphabet. The given sequence is R, M, I, F, D, ?, and you must find the next letter that continues the pattern.

Given Data / Assumptions:

• Series: R, M, I, F, D, ?
• Each term is a single letter.
• The pattern is based on alphabetical positions and differences between consecutive letters.
• Alphabet positions: A = 1, ..., Z = 26.

Concept / Approach:
We convert each letter into its numeric position and calculate the differences between consecutive terms. Often, such series involve a consistent decrease in steps that may themselves form a pattern (for example, decreasing by 5, 4, 3 and so on). Once we identify the rule, we apply it to the last known letter to obtain the missing one.

Step-by-Step Solution:
Step 1: Convert each letter to its position. R = 18, M = 13, I = 9, F = 6, D = 4. Step 2: Compute the differences between consecutive terms. 18 to 13: -5. 13 to 9: -4. 9 to 6: -3. 6 to 4: -2. Step 3: The differences are -5, -4, -3, -2. The pattern is that the negative step size increases by +1 each time (that is, it moves from -5 towards zero by one step). Step 4: Following this logic, the next difference should be -1. Step 5: Apply the next difference to the last known term: 4 + (-1) = 3. Step 6: Position 3 corresponds to the letter C.

Verification / Alternative check:
Rewrite the full sequence including the answer: R (18), M (13), I (9), F (6), D (4), C (3). The differences are -5, -4, -3, -2, -1. This is a smooth and natural pattern, so C is the only letter that completes the series correctly.

Why Other Options Are Wrong:
Option A (B): B is 2; 4 to 2 would be -2, repeating the previous difference instead of continuing the sequence -5, -4, -3, -2, -1. Option C (A): A is 1; 4 to 1 would be -3, which also breaks the consistent increment in the difference values. Option D (E): E is 5; 4 to 5 would be +1, completely reversing the direction of the series.

Common Pitfalls:
Test-takers often check only the letters and not the exact numeric differences. Another mistake is to assume a constant difference instead of checking whether the step sizes themselves may form a secondary pattern. Always calculate the differences carefully before deciding on the next term.

Final Answer:
The correct letter that completes the series is C, corresponding to option B.