单选题 .  U.S. Education Secretary Arne Duncan appealed Friday for a new generation of extraordinary teachers, calling education the civil rights cause of our time. Duncan told about 100 prospective (未来的) teachers at the University of Virginia that veterans, retirees and professionals seeking a second career must pay attention to the call to teach. He said the need is especially acute for black men in the nation's classrooms.
    The Virginia address is the first of several Duncan will make in October to press for bright candidates to enter teaching. He'll host a virtual town meeting with teachers from around the nation on Oct. 20, then deliver a major address on teacher preparation two days later in New York City.
    Duncan stressed the importance of teaching as the U.S. competes with an increasingly educated global work force, saying strong education is needed to reduce dropout rates among African-American, Latino and low-income students. "I believe that education is the civil rights issue of our generation," Duncan said. "If you care about promoting opportunity and reducing inequality and social injustice, the classroom is the place to start."
    Duncan noted that the next four years alone could see one-third of the nation's teachers and administrators leave. The departure of veteran educators will create huge demand for new teachers—200,000 annually in good economic times, he said.
    Duncan stressed that the demand for teachers is greatest among "high-poverty, high-needs" and rural schools, as well as in subjects such as math and science. "It is especially troubling," he added, "that less than 2 percent of our nation's teachers are African-American males."
    Duncan said the way to bring more young black men into the teaching profession is to make sure that they continue their studies and don't drop out at the high rates they do now. "Our African male dropout rate is too high. If you're dropping out of high school you can't be a teacher," he said.
    Duncan said the nation cannot rely alone on schools of education to produce the next generation of teachers. He called for expanding alternatives such as Teach for America, which recruits recent college graduates to teach in schools in poor communities for at least two years.1.  Duncan made the Virginia address so as to highlight ______.