It was originally built to defend an empire（帝国），but now parts of the Great Wall of China are crumbling（破碎 so badly they need someone to hurry to their defense.
 About 2,000 kilometers, or 30%，of the ancient fortification(防御工事) built in the Ming Dynasty has disappeared due to natural and human damage, according to the Beijing Times. And the situation could worsen, experts are warning as not enough is being done to preserve what remains.
   “It's a great pity to witness the Great Wall in such terrible situation ," Mei Jingtian, a volunteer who has worked for three decades to safeguard the structure and has founded the Great Wall Protection Association,tells CNN.
 About 8,000 kilometers of the structure dates from the Ming period between the 14th and 17th centuries and is considered by some to be the original Great Wall．Of this, 2,000 kilometers is made up of naturally occurring earthworks - and so only 6,000 kilometers of actual Ming dynasty wall was ever built.  Stretches(延伸)built in other eras make up a total length estimated up to 21,000 kilometers.
    Many visitors to china associate the Great Wall with a widely restored stretch of Ming era wall at Badaling  near Beijing, but this is far from typical of most of the structure.
 According to a 2014 survey done by the Great Wall of China Society, only about 8.2% of the Great Wall is in good condition, with74. 1% classified as poorly preserved, "The Great Wall is a vast heritage(遗产)site - over 20,000 kilometers - thus increasing the difficulty in preservation and restoration,” Dong Yaohui,  deputy director of the Great Wall of China Society, tells CNN.
    “Reliance on a very small amount of manpower by the local heritage departments is not enough to guard and protect the site."
    A recent increase in interest from tourists in visiting wild sections, known as the "Wild Great Wall," has accelerated its deterioration（恶化），according to the report.
21.  The present situation of the Great Wall is not optimistic due to the following reasons EXCEPT____.
    A．natural and human damage    B. limited preservation
    C. booming tourists visiting    D. wars between countries
22.  Which of the following is true about the original Great Wall?
    A. Not all of it is man-made Ming dynasty structure.
    B. It is made up of naturally occurring earthworks.
    C. Its length i8 estimated up t0 21,000 kilometers.
    D. It is in good condition and well-preserved.
23. What can we infer from what Dong Yaohui said?
    A. The Great Wall is well protected.
    B. The preservation and restoration is difficult.
    C.  The local heritage departments didn't do their job.
    D. The government should do more with the protection.
24. What is the article mainly about?
    A. The Great Wall and its glorious history.    B. Tourists' visiting to the Great Wall.
    C. The Great Wall and its worrying condition.    D. The functions of the Great Wall.

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