Choose the 4-letter fill that preserves the alternating density of b/c around stable “ccbab … caa … bccc … a …” anchors: ccbab _ caa _ bccc _ a _

Introduction / Context:
The anchors “ccbab”, “caa”, “bccc”, and “a” suggest an alternation of b and c around fixed clusters. The correct 4-letter fill should keep a balanced b/c density without producing triple runs or disrupting the anchor shapes.

Given Data / Assumptions:

• Template: ccbab _ caa _ bccc _ a _
• Four letters are inserted sequentially.
• We must avoid “bbb” or “ccc” triple runs at the seams.

Concept / Approach:
Pick a fill that starts with b (to pair after “…ccbab”), introduces an a only where a is already anchored, and alternates b/c on each side of “bccc”.

Step-by-Step Solution:

Verification / Alternative check:
Other choices either cause “bbb/ccc” near anchors or place “a” in disruptive positions.

Why Other Options Are Wrong:

• babb: Creates “bbbb” risk close to “…bccc”.
• bbba: Triple b appears against “bccc”.
• baab: Misplaces “a” away from its anchor, breaking symmetry.
• None of these: Not necessary since “babc” fits.

Common Pitfalls:
Inserting extra “a” far from “caa” anchor; overlooking triple-seam collisions.

Final Answer:
babc