Insert five letters to maintain the “b anchors between a/c swings” rule across the whole run: b _ ac _ cc _ cb _ ab _ ac

Introduction / Context:
The given skeleton fixes “ac/cc/cb/ab/ac” as internal anchors. A good completion keeps b as a recurring anchor between alternating a/c swings, avoiding triple same-letter runs at seams.

Given Data / Assumptions:

• Template: b _ ac _ cc _ cb _ ab _ ac
• Five letters inserted sequentially.
• Avoid clusters like “aaa”, “bbb”, “ccc”.

Concept / Approach:
We want a pattern that starts by pairing b with c (to lead into “…bac…”), then toggles a/b to support “…cc…” and “…cb…”, finally closing cleanly before the last “…ac”.

Step-by-Step Solution:

Verification / Alternative check:
Other options either introduce “bbb” or mis-time the c near the “…cc…” anchor, causing collisions.

Why Other Options Are Wrong:

• bbaac: Packs double b’s against “cb/ab” anchors.
• abbbc: Creates “bbb”.
• aabba: Misaligns with “…cc…” and “…cb…” placements.
• None of these: Not required since “cbaba” works.

Common Pitfalls:
Forgetting to check every seam; a candidate can look fine up front yet fail near the close.

Final Answer:
cbaba