Develop your reading skills. Read the following text and do the comprehension question
The Great Wall Of China
The Great Wall of China, one of the greatest wonders of the world, was first built between 220–206 BC. In fact, it began as independent walls for different states when it was first built, and did not become the "Great" wall until the Qin Dynasty. Emperor Qin Shihuang succeeded in his effort to have the walls joined together to serve as fortification to protect the northern borders of the Chinese Empire from invasion. Afterwards it was rebuilt and maintained over the years, between the 5th century BC and the 16th century.
One of the myths associated with the Great Wall of China is that it is the only man-made structure that can be seen from the moon with the naked eye. The legend originated in Richard Halliburton's 1938 book Second Book of Marvels. However, This myth is simply not true. Richard Halliburton's claim was contradicted by astronauts Neil Armstrongby and Yang Liwei. A more plausible assumption would be to say that the Great Wall can be visible from a low orbit of the earth which is not unique in this regard as many other artificial constructions can be seen from that height.