Difficulty: Medium
Correct Answer: cabca
Explanation:
Introduction / Context:Many letter-series items rely on a rotation over a small alphabet subset (here {a, b, c}). The goal is to restore the same rotation across the entire sequence.
Given Data / Assumptions:
Concept / Approach:We attempt fills that recreate a consistent cycle such as c→a→b or a→b→c. After inserting a candidate, verify each 3-letter window matches the rotation (e.g., b→c→a or c→a→b, etc.).
Step-by-Step Solution:
1) Insert option d (c a b c a) in the blanks, left to right.2) The resulting line supports a smooth c→a→b (and its shifts) cycle throughout without contradictions at the junctions.3) Other options produce at least one break where the next letter in the cycle does not match the expected successor.Verification / Alternative check:Traverse the series and check every triple: each respects the same rotated order.
Why Other Options Are Wrong:
Common Pitfalls:Assuming local adjacency is enough; ensure the same rotation governs the entire line.
Final Answer:cabca
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