So far, people have invented so many things that has changed our life 1 . The first great invention was the one that is still very 2 today—the wheel. This made it easier for us to carry heavy things and 3 long distances.
For hundreds of years after that, there were few inventions that had as much effect (影响) as the wheel. Then in the early 1800s, the world started to 4 . There was little unknown land in the world. People did not have to explore (探索) much any more. They began to work in order to make life 5 . During the second half of the 19th century, many great inventions were made. Among 6 were the electric light and the radio. These all became big parts of our life today.
In the first part of the 20th century, more 7 inventions appeared: the helicopter (直升机), jet plane and movies with sound. This was also the 8 when a new material (材料) was first made. Nylon (尼龙) 9 in 1935. It changed the kind of 10 people had been wearing.
