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]: kurt julius isselbacher (september 12, 1925 – july 18, 2019) was a german-born american physician and gastroenterologist.
[A]: kurt julius isselbacher


[Q]: jujutsu (柔術, jūjutsu) is an ancient japanese martial art.
[A]: jujutsu


[Q]: the four great inventions are the four most important inventions in the history of china.
[A]:
four great inventions