完形填空。 We can see walls everywhere in the world . But the Great Wall of China is the 1 of all. The Chinese call it 'the Ten-thousand-li Great Wall'. It is more than 6,000 kilometers. It is 4-5 meters 2 . In most places, five horses or ten 3 can walk side by side. When you visit the Great Wall, you can't 4 wondering how the Chinese were able to build such a great wall thousands of years ago. 5 any modern machines, it was really very difficult to build it. They 6 to do all the work by hand. It 7 millions of men hundreds of years to build it. The Great Wall has a history of over two thousand years. The king began to build the first parts of it around two thousand seven hundred years 8 . Then Qin Shihuang had all the walls joined up. He thought that could keep the 9 out of the country. Today the Great Wall has become a place of interest. Not only the Chinese people 10 people from all over the world come to visit it. (     )1. A. smallest (     )2. A. wide (     )3. A. farmers (     )4. A. think (     )5. A. Without (     )6. A. must (     )7. A. cost (     )8. A. before (     )9. A. enemy (     )10. A. but B. highest B. tall B. men B. ask B. With B. could B. spent B. ago B. friend B. also C. biggest C. long C. visitors C. help C. In C. might C. took C. after C. thief C. and D. longest D. deep D. workers D. do D. Under D. had to D. worth D. then D. people D. but also