三、完形填空
A team of Chinese scientists have found a new giant sinkhole (天坑). It's 192 metres ______1______. What did they find at the ______2______? An ancient forest!
This ______3______ discovery was found in Leye County, Guangxi Zhuang autonomous region. Leye County is famous ______4______ "the museum of sinkholes". People ______5______ about 30 sinkholes there before.
How do sinkholes form?
The karst landform (喀斯特地貌) is widely distributed (分布) in China. The karst landform is made when rainwater runs through little holes ______6______. These holes ______7______ grow into a cave. Over time, the cave can get so ______8______ that its top falls down slowly, opening up a sinkhole. The sinkholes in China are called wonders by George Veni, an expert in this field, because of ______9______ great sizes.
______10______ are sinkholes important?
Besides looking cool, karst caves and sinkholes can be the ______11______ to many kinds of plants, animals and microbes. "I won't be surprised to know that some species (物种) in these caves have never been ______12______ or described by science until now," said the leader of the Chinese scientists who study sinkholes, Chen Lixin. This is ______13______ the sinkholes are unknown to the outside world. That ______14______ an environment for new species to form.
Sinkholes also hold lots of underground water. They are like water pipes in nature. They bring ______15______ to 700 million people worldwide.
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