A、Movies with sound. B、Nylon. C、The radio. D、The computer. C19 世纪后半期，许多伟大的发明出现了，有照相机，电灯和无线电。

There have been many great inventions, things that change the way we live. The first great invention was one that is still very important today — the wheel. This made it easier to carry heavy things and to travel long distances.
For hundreds of years after that there were few inventions that had as much effect as the wheel. (23) Then in the early 1800’s the world started to change.
There was little unknown land left in the world. People did not have to explore much any more. They began to work instead to make life better. (24) In the second half of the 19th century many great inventions were made. Among them were the camera, the electric light and the radio. These all became a big part of our life today. The first part of the 20th century saw more great inventions.
The helicopter in 1909. Movies with sound in 1926. The computer in 1928. And jet planes in 1930. This was also a time a new material was first made. Nylon came out in 1935. It changed the kind of clothes people wear.
(25) The middle part of the 20th century brought new ways to help get over diseases. They worked very well. They made people healthier and let them live longer lives. By the 1960’s most people could expect to live to be at least 60. By this time most people had a very good life. Of course new inventions continued to be made. But man now had a desire to explore again. The world was known to man but the stars were not, man began looking for ways to go into space. Russia made the first step. Then the United States took a step.
Since then other countries, including China and Japan, have made their steps into space. In 1959 man took his biggest step away from earth. Americans first walked on the moon. This is certainly just a beginning though. New inventions will someday allow us to do things we have never yet dreamed of.
Questions 23 to 25 are based on the passage you have just heard.
23. When did people stop exploring a lot?
24. Which was an important invention in the 19th century?
25. What made people healthier and let them live longer lives in the middle part of the 20th century?