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: How many years had Ernest Lawrence worked at UCLA before Backus attended? Passage:John Backus was born and raised in Portland, Oregon, where he studied at Reed College, receiving a BA in 1932. He went on to graduate studies at the University of California, Berkeley, where he did research in nuclear physics at the Radiation Laboratory under Ernest Lawrence. He received an MA in 1936, and a PhD in 1940. In 1945 he was appointed Professor of Physics at the University of Southern California, a post he retained until his retirement in 1980. During the early part of his career, his research focussed on gaseous discharges in strong magnetic fields. He was also a musician, trained as a performer on piano, bassoon, clarinet and other woodwinds and received the degree of MMus in conducting from the University of Southern California in 1959. In his later career he turned increasingly to the study of musical acoustics, particularly those of wind instruments and organ pipes. In 1969 he published The Acoustical Foundations of Music, a book which became a standard text for introductory courses in musical acoustics. A second edition appeared in 1977. He received the Silver Medal of the Acoustical Society of America in 1986. Backus died in Los Angeles in 1988.
Links: a. Woodwind instrument b. Los Angeles c. Ernest Lawrence d. Musical acoustics
c