Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

[EX Q]: chelers is a commune.
[EX A]: chelers

[EX Q]: ans is a municipality in the belgian province of liège.
[EX A]: ans

[EX Q]: hawking radiation is black body radiation which is emitted by black holes, due to quantum effects near the event horizon.
[EX A]:
hawking radiation