Choose a 4-letter ordered set to complete: m _ m _ am _ a _.

Introduction / Context:
We must place four letters into a short skeleton using {a, m}. The visible clusters include “m m” and “am”, suggesting the motif “ma/ma”.

Given Data / Assumptions:
Skeleton: m _ m _ a m _ a _ (4 blanks). Options: amam, ammm, amaa, mama.

Concept / Approach:
A natural completion is to alternate m and a to form repeating “ma” blocks while preserving the fixed “am” already present.

Step-by-Step Solution:
1) Insert “m a m a”.2) This yields “…m m m a a m m a a…”, aligning multiple “ma” transitions and keeping the given “am” intact.3) Other options either over-concentrate m’s (“ammm”), create long a-runs (“amaa”), or misplace alternation (“amam”).

Verification / Alternative check:
Scan for consistent “m→a→m→a” alternation.

Why Other Options Are Wrong:
They introduce triple m’s or double a’s that are not implied by the skeleton.

Common Pitfalls:
Choosing by majority letter rather than alternation logic.

Final Answer:
mama