题目

Anyone who cares about what schools and colleges teach and how their students learn will be interested in the memoir（回忆录）of Ralph W. Tyler, who is one of the most famous men in American education. Born in Chicago in 1902, brought up and schooled in Nebraska, the 19-year-old college graduate Ralph Tyler became hooked on teaching while teaching as a science teacher in South Dakota and changed his major from medicine to education. Graduate work at the University of Chicago found him connected with honorable educators Charles Judd and W. W. Charters, whose ideas of teaching and testing双曲线=1(mn≠0)的离心率为2,有一个焦点与抛物线y2=4x的焦点重合,则mn的值为(    )A.              B.              C.             D.