The sentence is: A small __________ between two children escalated into a group fight.
Evaluating the options to fill the blank:
- Altercation: A noisy argument or disagreement. This aligns with a conflict that could lead to a fight.
- Match: A game or competition. This does not fit the context of leading to a fight.
- Contest: Similar to a match, implying competition rather than conflict.
- Race: A speed competition, unrelated to arguments or fights.
Based on the definitions, "altercation" is the most suitable word.
Therefore, the completed sentence is: A small altercation between two children ended up as a group fight.