A、He still led the Eight-year Study. B、He called for free spirit in research. C、He was still active in giving advice. D、He devel

Anyone who cares about what schools and colleges teach and how their students learn will be interested in the memoir 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 had an effect on his later work. In 1927, he became a teacher of Ohio State University where he further developed a new method of testing.
    Tyler became well-known in 1938, when he carried his work with his Eight-year Study from Ohio State University to the University of Chicago at the invitation of Robed Hutchins.
    Tyler was the first director of the Center for Advanced Study in the Behavioral Sciences at Stanford, a position he held for fourteen years. There, he firmly believed that researchers should be free to seek an independent spirit in their work.
    Although Tyler officially retired in 1967, he never actually retired. He served on a long list of educational organizations in the United States and abroad. Even in his 80s he travelled across the country to advise teachers and management people on how to set objectives that develop the best teaching and learning within their schools.
Questions 30 to 32 are based on the passage you have just heard.
30. Who are most probably interested in Ralph W. Tyler’s memoir?
31. Where did Tyler work as the leader of a research center for over 10 years?
32. Why is Tyler said to have never actually retired?