A. transport B. spread C. wheels desire D. development E. tool

We do not know when people invented wheels. But once it was invented, knowledge of the wheel ______ quickly across the world. It is easy to move things with wheels. The first example of wheels dated from about 3,500 to 3,000 BC. The cart or wagon was the first vehicle which had wheels. At that time, they were pulled by humans or animals. Today, there are still carts drawn by animals in many countries. These carts are mainly used to move things or ______ people. Around 2,000 BC, the chariot（双轮敞蓬马车）appeared. It moved even faster than the cart, so it soon became an important ______ in the war and later was introduced to other ancient countries, such as Egypt, Persia, Greece and Rome.

The invention of wheels is very important to the ______ of new transportations. Without wheels, the invention of bicycles, motorcycle, cars, trains, and planes may not be possible.

【1】________

【2】________

【3】________

【4】________