Which of the following words is often used to mean the lifework of a writer, artist or composer?

The term "oeuvre" is used to describe the complete body of work completed by a writer, artist or composer throughout their career. The word is borrowed from French, literally meaning "work". It stems from Old French "over", meaning "activity, effort, attention or work". The first known use of the word was in 1889.

A "Magnum opus" is the greatest achievement of a writer, artist or composer. The word "opus" also means "work" but "magnum" means greatest. This term predates "oeuvre" by almost a century.

"Adhésion" has little to do with art, music or literature. It is the French term for "adhesion", meaning to stick together. "Rassemblement" is also a French word. It means "gathering" or "bringing together".