Step 1: Timeline check.
WWII ended in 1945. NATO was founded in 1949—therefore post-WWII.
Step 2: Why others are wrong.
Treaty of Versailles (A) and League of Nations (D) are post–World War I outcomes (1919–1920).
Russian Revolution (B) occurred in 1917.
Step 3: Conclude.
\[
\boxed{\text{NATO’s establishment (Option C) happened after WWII.}}
\]