In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: What year was the School of American Ballet founded? Passage:Waring's training began in 1939 in San Francisco and Oakland at the age of 17. He was exposed to numerous kinds of dancing, including ballet at the San Francisco Ballet School with Harold Christensen and his brother, the Graham technique with Gertrude Schurr, and the interpretive dance of Raoul Pause. Later, after serving in the Army in World War II, he studied in New York City at the School of American Ballet, and with Anna Halprin, Louis Horst, Antony Tudor, and Anatole Vilzak, and also took some classes with Merce Cunningham. Waring was very attracted to ballet and intrigued by its complex history and sensibility, and dance historian David Vaughan suggests that Waring's extensive knowledge of dance history played an important role in his work; Waring's dances became more balletic over time.
Links: a. School of American Ballet b. Anna Halprin c. World War II d. World War II
a