In the alphabet series QAR, RAS, SAT, TAU, ?, find the next three letter group that completes the pattern.

Introduction / Context:
This problem involves recognising a pattern within three letter alphabetic groups. Each position within the group can follow its own sequence. The task is to track how the first, second and third letters progress and then combine those patterns to determine the missing term.

Given Data / Assumptions:

• Given groups: QAR, RAS, SAT, TAU, ?
• We treat each group as three independent letter positions.
• The rule that generates earlier groups is assumed to continue in the same way.

Concept / Approach:
For such series, the best strategy is to write each group in vertical columns: first letters together, second letters together and third letters together. Then we inspect how each column changes across the series. Normally we see simple alphabetic sequences such as increments by one position.

Step-by-Step Solution:
Step 1: First letters: Q, R, S, T. These are consecutive letters in forward order, so the next first letter is U.Step 2: Second letters: A, A, A, A. The second position remains fixed at A for every group, so the next second letter is also A.Step 3: Third letters: R, S, T, U. These are also consecutive letters moving forward by one each time, so the next third letter is V.Step 4: Combining all three positions, the missing group is U A V, written as UAV.

Verification / Alternative check:
If we rewrite the pattern clearly, we get: first column Q R S T U, second column A A A A A, third column R S T U V. Both the first and third columns form straightforward alphabetical sequences. There is no sign of any other consistent pattern that contradicts UAV, so the answer is stable.

Why Other Options Are Wrong:
UAT, UAS and UTS all preserve U as the first letter, but their third letters break the simple forward sequence R, S, T, U, V. Any option that does not use V as the third letter fails the observed pattern. TAV changes multiple positions at once and is inconsistent with all three columns examined together.

Common Pitfalls:
Learners sometimes try to treat each three letter group as a single unit and search for complex transformations, instead of separating the positions into columns. For many exam questions of this type, breaking the series into columns reveals three very simple sequences, which is the case here.

Final Answer:
The three letter group that correctly completes the series is UAV.