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]: police action is a term for the use of military forces without declaring war.
[EX A]: police action

[EX Q]: the beethoven house (german: beethoven-haus) in bonn, germany, is a memorial site, museum and cultural institution serving various purposes.
[EX A]: beethoven house

[EX Q]: a session key is a single-use symmetric key used for encrypting all messages in one communication session.
[EX A]:
session key