Difficulty: Medium
Correct Answer: acba
Explanation:
Introduction / Context:
A final a/b/c template puzzle using anchors like “bbc”, “aab”, “cca”, and “bbcc”. We must insert four letters to keep the internal structure and produce clean transitions.
Given Data / Assumptions:
Concept / Approach:
Look for a fill that lightly separates anchors with single letters while avoiding triple runs. The aim is to respect “bbc” → “aab” → “cca” → “bbcc”.
Step-by-Step Solution:
Insert "acba": a a bbc c aab a cca a bbcc. The joins are neat: a|bbc, c|aab, a|cca, a|bbcc, with no broken anchors.
Verification / Alternative check:
Other fills scramble the joins—either fusing anchors or inserting letters that fracture them.
Why Other Options Are Wrong:
bacb / abba / caba: Each introduces at least one problematic join around “aab” or “cca”.
Common Pitfalls:
Treating each blank independently instead of validating the entire chain of anchors.
Final Answer:
acba
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