Insert six letters (grouped as shown) to preserve the “a…b…a…” motif while bridging an “n” and the “bb…abbn” tail: a__b__a__ __n__bb__abbn

Introduction / Context:
This item combines the familiar “a…b…a…” motif with an embedded “n” and a fixed “bb…abbn” tail. The chosen fill must bridge to the “n” cleanly and arrive at the tail without triple clashes.

Given Data / Assumptions:

• Scaffold: a __ b __ a __ __ n __ bb __ abbn
• Six letters inserted in the grouped blanks (left-to-right).
• Avoid “aaa/bbb”.

Concept / Approach:
We need an early “ab” to support the a–b–a arc, a mid “n” connector, and a late “abb” to align to “…abbn”. The option “abnabb” encodes exactly that progression.

Step-by-Step Solution:

Verification / Alternative check:
Other candidates either misplace n or cause triple b’s before the tail.

Why Other Options Are Wrong:

• bnbban / bnbbna / babban: Either mis-time n or overload b’s.
• None of these: Not necessary.

Common Pitfalls:
Handling the n too early or too late and colliding with the “bb…abbn” tail.

Final Answer:
abnabb