A、Inventions. B、Demands in marketplace. C、Ongoing economic growth. D、Education. C对话中，女士谈到了有很多推动社会变化的因素，其中最重要的动力是持续的经济增长。这与C项的表述一

M: Well, were there other forces which pushed the social changes?
W: Education was another important force. More and more Americans were getting a good education. The number of students attending high school doubled between nineteen twenty and nineteen thirty. Attendance at colleges and universities also increased greatly. Two inventions, the automobile and the radio also helped cause the social changes. The automobile gave millions of Americans the freedom to travel easily to new places. And the radio brought new ideas and experiences into their own homes. Probably the most important force was the continuing economic growth of the nineteen twenties. Many people had extra money to spend on things other than food, housing, and other basic needs. They could experiment with new products and different ways of living.
M: Had lives of American people been changed a lot?
W: Of course not everyone’s life had been changed. Millions of Americans in small towns or rural areas continued to live simple, quiet lives. Life was still hard for many people including blacks, foreigners, and other minority groups. Many newspaper stories about independent women reporters and doctors also did not represent the real life of the average American woman. Women could vote. But three of every four women still worked at home. Most of the women working outside their homes were from minority groups or foreign countries.
M: Did people have any special interest in that background?
W: Well, people had wide interest during the nineteen twenties. People became extremely interested in exciting court trials, disasters, film actors, and other subjects. For example, millions of Americans followed the sad story of Floyd Collins, a young man who became trapped while exploring underground. Newsmen reported to the nation as rescue teams searched to find him. Even the "New York Times" newspaper printed a large story on its front page when rescuers finally discovered the man’s dead body.
M: Americans are crazy about sports now. American football, baseball and basketball are the three most popular sports, and billions of people watch these matches every year. Were people interested in sports during the nineteen twenties? Who was the most famous sports star?
W: The nineteen twenties were a golden period for sports. People across the country bought newspapers to read of the latest golf victory by champion Bobby Jones. "Big Bill" Tilden became the most famous player in tennis. And millions of Americans listened to the boxing match in nineteen twenty-six between Jack Dempsey and Gene Tunney. However, the greatest single sports hero of the period was the baseball player, Babe Ruth. Ruth was a large man who could hit a baseball farther than any other human being. He became as famous for his wild enjoyment of life as for his excellent playing on the baseball field.
M: OK, thank you for talking to us in the studio. The nineteen twenties was also a time of much excellent work in the more serious arts. We will take a look in our next program at American art, writing, and building during the exciting "roaring twenties".
6. In Professor Smith’s view, what was the most important force that pushed the social changes?
7. What do we learn about changes in lives of American people?
8. What do we know about the sad story of Floyd Collins?
9. Who was the greatest single sports hero in the 1920s?
10. What will be discussed in the following program?