Why Was the Group of Intellectuals That Left the United

Why was the group of intellectuals that left the United States for Europe in the 1920s called the "lost generation"?

A) They were disillusioned with the emptiness of mainstream middle-class culture.
B) They had no prospects in the American economy of the 1920s.
C) As a result of their self-chosen exile, their cultural productivity waned.
D) Over time, this intellectual community of ex-pats disappeared in the European middle class.