In the alphabetic series PBA, QCB, RDC, SED, which group of three letters should come next in order to continue the pattern correctly?

Introduction / Context:
This is an alphabet series question that appears in many aptitude and reasoning tests. The goal is to identify the pattern that connects successive groups of letters and then extend that pattern to find the missing term. These problems train observation, pattern recognition, and systematic thinking about positions of letters in the English alphabet.

Given Data / Assumptions:
We are given a sequence of three letter groups:
PBA
QCB
RDC
SED
We need to determine the next group of three letters.
We use standard English alphabet positions, where A is 1, B is 2, and so on up to Z which is 26.

Concept / Approach:
The usual approach is to separate each term into first, second, and third letters and then analyse how each position changes from term to term. Very often in such series, each position follows its own incremental pattern. By calculating the progression for each position independently, we can derive the next letters logically instead of guessing.

Step-by-Step Solution:
Step 1: Write the first letters of each term: P, Q, R, S. Step 2: Observe that P, Q, R, S are consecutive letters. So the next first letter after S is T. Step 3: Write the second letters of each term: B, C, D, E. These are also consecutive letters. So the next second letter after E is F. Step 4: Write the third letters of each term: A, B, C, D. These again form a consecutive series. So the next third letter after D is E. Step 5: Combine the three next letters to form the missing group: T, F, and E, which gives TFE.

Verification / Alternative check:
We can verify our observation by re checking each position. The first position moves P, Q, R, S, T. The second moves B, C, D, E, F. The third moves A, B, C, D, E. In all three positions the pattern is consistent and strictly increasing by one letter each time, so TFE is the only term that preserves the structure of the sequence.

Why Other Options Are Wrong:
TFD: The third letter D does not continue the third letter pattern A, B, C, D, E.
TGE: The second letter G breaks the B, C, D, E, F sequence, and the third letter E is only partly correct.
RST: None of the letters in this option follow the individual positional patterns found in the original sequence.
None of these: This is incorrect because we have already identified TFE as a valid continuation of the pattern.

Common Pitfalls:
A frequent mistake is to focus only on one letter position or to look for a more complex pattern than necessary. Another error is to treat the three letters together as one unit without analysing each position separately. In many reasoning questions, a clean solution appears once you split the pattern by positions.

Final Answer:
The next group of letters in the series is TFE.