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.

Q: ans is a municipality in the belgian province of liège.

A: ans
****
Q: stinging nettles ("urtica dioica") are a type of plant which have stinging defensive hairs on the leaves and stems.

A: stinging nettle
****
Q: london heathrow airport, or heathrow, is the main, and busiest airport serving the united kingdom.

A:
heathrow airport
****