A letter series is given with one term missing. Select the correct group of letters that will complete the sequence: CAT, DBT, ECT, ?

Introduction / Context:
This is a straightforward alphabetical series question where you must identify the pattern in each letter position of three-letter groups and then find the next group that fits that pattern. The sequence is CAT, DBT, ECT, ?, and you have to determine which option correctly replaces the question mark.

Given Data / Assumptions:

• Given series: CAT, DBT, ECT, ?
• Each term has three letters.
• The pattern is presumed consistent across all three letter positions.
• Alphabet positions: A = 1, B = 2, ..., Z = 26.

Concept / Approach:
We treat the first, second and third letters in each group as separate sequences. For each position, we convert letters to numerical positions, look for a regular pattern (such as +1), and then apply that rule to predict the next letter. Once all three letters are determined, we match the result with the given options.

Step-by-Step Solution:
Step 1: First letters of each term: C, D, E. Convert to positions: C = 3, D = 4, E = 5. This is a simple +1 pattern. Step 2: The next first letter after E (5) is 5 + 1 = 6, which is F. Step 3: Second letters: A, B, C. Positions: A = 1, B = 2, C = 3, again increasing by +1. Step 4: The next second letter after C (3) is 3 + 1 = 4, which is D. Step 5: Third letters: T, T, T. All terms end with T, so the third letter remains constant. Step 6: Combine the three results: first letter F, second letter D, and third letter T. The missing term is FDT.

Verification / Alternative check:
We can rewrite the complete series with positions: CAT (3,1,20), DBT (4,2,20), ECT (5,3,20), FDT (6,4,20). Each column shows a clear pattern: the first column increases by 1, the second column increases by 1 and the third column is constant at 20 (T). Therefore FDT is fully consistent with the established pattern.

Why Other Options Are Wrong:
Option A (DCT): The first letter D returns to 4 instead of moving forward to 6. Option C (FCT): The second letter C is 3, but it should have progressed to D (4). Option D (FAT): The second letter A is 1, which breaks the simple ascending pattern seen in the second position.

Common Pitfalls:
Sometimes candidates focus only on the first letter and ignore the rest of the pattern, leading to wrong choices. Another common issue is not checking every position separately. To avoid mistakes, always inspect each letter position as its own mini-series and then ensure that all positions fit a consistent rule.

Final Answer:
The term that correctly completes the series is FDT, which is option B.