There have been many great inventions, which have changed 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 to travel long distances. For hundreds of years after that there were few inventions that have made as much effect as the wheel. There was little unknown land left in the world. People didn't have to explore(开发) much any more. They began to work instead to make life better.
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. Sound movies in 1926. The computer in 1928, and jet planes in 1930. This was also a time when a new material was made. Nylon came out in 1935. It changed the kind of clothes people wear. The middle part of the 20th brought new ways to help people get over diseases. They worked very well. They made people healthier and let them live long lives. By the 1960s 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 wish to explore again. The world is known to man but the stars are not yet. 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.
49. Which of the following was turned out nearly at the same time with the jet plane?
A. The radio. B. The camera. C. Nylon. D. The helicopter.
50. This passage talks mainly about ______.
A. how inventions affect (影响) people's life B. when electric light was invented
C. which country made the first step into space D. why cars were very important
51. We can safely come to the conclusion that people's life will be made even better through ______.
A. new discoveries B. greater inventions
C. better ways to help people get over diseases D. all of above