Step 1: Expand the acronym accurately.
NATO expands to North Atlantic Treaty Organization—a collective-defense alliance founded by the 1949 North Atlantic Treaty.
Step 2: Eliminate close-sounding distractors.
There is no ``North {Arctic}'' or ``North {Asian}'' treaty organization; ``North {American}'' would exclude Europe, which is incorrect.
Step 3: Conclude.
\[
\boxed{\text{North Atlantic Treaty Organization (Option A).}}
\]