Read the following passage, and answer the questions:
THE GREAT WALL OF CHINA
In China, there is a wall that is 1,500 miles long. It is called the Great Wall of China. It winds uphill and down, through valleys and mountains. It was made by hand. The Great Wall of China was built from 246 to 209 BC. The people of China made it to keep out their enemies. There are watch towers all along the way. The Wall is made of brick and earth. It is high and wide on top. People can walk along the top as if it were a road. No other defense line has ever been made as long as the Great Wall of China.
What is the purpose of the Great Wall?
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Đáp án: It was made to keep out their enemies.