Many of China's ancient architectural treasures crumbled to dust before Lin Huiyin and Liang Sicheng began documenting them in the 1930s. The husband and wife team were by far the best-known __ to operate in China.Their __ have since inspired generations of people to speak out for architecture threatened by the rush toward development.

Becoming China's first architectural historians was no easy____.The buildings they wanted to___ were centuries old, often in shambles and located in distant parts of the country. In many cases, they had to journey through ___conditions in the Chinese countryside to reach them.     

___China's outlying areas during the 1930s meant traveling muddy, poorly maintained roads by mule, or on foot.This was a(n)____undertaking both for Liang,who walked with a bad limp(跛）after a motorcycle accident as a young man, and Lin,who had a lung disease for years. Inns were often unimaginably dirty,food could be tainted(污染的），and there was always __ of violence from rebels,soldiers and bandits.

Their greatest discovery came on an expedition in 1937 when they dated and extremely____catalogued Foguang Si, or the Temple of Buddha's Light, in Wutai County,Shanxi Province. The breathtaking wooden temple was____in 857 A.D.,making it the oldest building known in China at the time. (It is now the fourth-oldest known).

Liang and Lin crawled into the temple's most____areas to determine its age, including one aerie inhabited by thousands of bats and millions of bedbugs, covered in dust and littered with dead bats. Liang wrote of the____in an account included in "Liang and Lin:Partners in Exploring China's Architectural Past," the English-language story of their lives written by Wilma Fairbank,their close friend and correspondent.

＂In complete darkness and amid the___smell, hardly breathing, with thick masks covering our noses and mouths,we measured,drew,and photographed with flashlights for several hours,"Liang wrote."When ___we came out to take a breath of fresh air, we found hundreds of bedbugs in our backpack.We ourselves had been badly bitten.Yet the____and unexpectedness of our find made those the happiest hours of my years hunting for ancient architecture."

Usually when another old cave is discovered in the south of France, it is not news. Rather, it is an ordinary ________. Such discoveries are so ________ these days that hardly anybody ________ them. ________, when the Lascaux cave complex was discovered in 1940, the world was ________. Painted directly on its walls were hundreds of ________ showing how people lived thousands of years ago, most of which were about people ________ animals, such as wild cats or dogs. Other images picture animals, ________ horses, which appear in more than 300 wall images by far ________ all other animals.

Early artists drawing these pictures finished a difficult but ________ task. They did not limit themselves to the easily ________ walls but carried their painting materials to spaces that required climbing high walls or going into narrow ________ in the Lascaux complex. ________, the paintings have been ________ to the destructive action of water and temperature changes, which easily ________ the images. Because the Lascaux caves have many entrances, air movement has also damaged the images ________.

Although they are not out ________, where natural light would have destroyed them long ago, many of the images are in bad condition and are ________ recognizable. Therefore, the place was closed to ________ in 1963, 23 years after it was discovered, to prevent further ________.

The impressive collection of literature in the Library Cave at the Mogao Caves in Dunhuang, Northwest China’s Gansu province, ______ one of the most inclusive, advanced and open _______ of the ancient Chinese, says Dunhuang specialist Zhao Xiaoxing.

______ in the Hexi Corridor, the main line of the ancient Silk Road, the caves, a UNESCO World Heritage Site, have been promoting goods and cultural ______between the East and the West for more than 1,600 years.

While the Dunhuang wall paintings have recorded the glories of the past ______ , the more than 60,000 items of literature______ in the Library Cave, or Cave 17, dating from the 4th to the 11th centuries, have kept the ______ original quality through the written word, according to Dunhuang Academy.

The value of the ______ was thoroughly demonstrated during the launch of the Digital Library Cave, a gamelike program ______ enables users to virtually witness, and participate in, the_________ and fall of the Library Cave on the website Digital Dunhuang or via the WeChat miniprogram, Cloud Museum of Dunhuang Caves.

The Library Cave ______ in the mid-9th century and later______ unopened for almost 1,000 years ____ being accidentally discovered by Taoist priest Wang Yuanlu in 1900.The majority of its cultural relics, consisting of Buddhist manuscripts, ______ and economic documents and other delicate and ______items, are now kept in foreign museums.