1 . Susan Sontag (1933-2004) was one of the most noticeable figures in the world of literature. For more than 40 years she made it morally necessary to know everything — to read every book worth reading, to see every movie worth seeing. When she was still in her early 30s, publishing essays in such important magazines as Partisan Review, she appeared as the symbol of American culture life, trying hard to follow every new development in literature, film and art. With great effort and serious judgment. Sontag walked at the latest edges of world culture.
The underlined sentence in paragraph 1 means Sontag_________.

A．was a symbol of American cultural life

B．developed world literature, film and art

C．published many essays about world culture

D．kept pace with the newest development of world culture