A. reflects the benefits provided by the sharing economy

B. was the most popular character for international issues for 2017

C. was selected as the phrase of the year for domestic issues

D. was recommended by all the internet users

21. If you want to express your original ambition, you can use the word or phrase __________.

A. Gui. B. Chuxin. C. Zhi. D. Xiang.

　　China's high-tech buildings can be seen everywhere in places like Beijing and Shanghai, but a few hundred miles away in Shanxi province, some three million people still live in caves.

　　These simple homes often dot the countryside in small, hard-to-find groups, but in places like Lijiashan, where hundreds of caves are on nine different levels of a hillside, it is possible to find whole villages made up entirely of cave livers.

　　People have been living in caves in Shanxi for around 5,000 years, and it is believed that at one time a quarter of the population lived underground. These days around one-twelfth live in caves and for many of them, life is almost as it was for their ancestors.

　　Lijiashan, a 550-year-old cave village is typical. Like most cave villages, there is still no running water, meaning locals are using muddy water of the nearby Yellow River. Most homes still have paper windows rather than glass ones. Inside, their owners sleep on large stone beds, known as kang; cool in the summer, but fires can be lit inside them during the winter months.

Lijiashan once housed 600 families. But now there are just over 40. Mr Li's family has lived in Lijiashan for six generations. After his kids left the village to find work elsewhere, he and his wife turned their 180-year-old home into a guest house with cave bed-rooms where Chinese art students stay when they come to paint the unusual village landscape.

"The only people left here now are old people," he said, "As soon as the children