From the “Roman Warm Period” to the “Little Ice Age” that began in the 14th century, periods of hot and cold weather    1     (extend) for centuries. As a result, many have argued that the current period of global warming    2    (be) part of a natural pattern and the human role in creating    3     has been exaggerated.

This new study suggests that is not    4     case. Scientists reconstructed the major climate events of the past 2,000 years by looking around 700 records, tree rings, ice cores and lake sediments(沉淀物)     5     (include). Not one single event affected as much of the world    6    the present period of warming is now doing. Other scientists    7     have looked at the study have been impressed by the quality of the research.

The researchers involved argue that the new     8     (finding) reveal many theories put forward by climate scientists    9     (explain) the rise in temperatures, including changes in solar activity. The current period of climate change is mainly down to humans, they insist. Natural causes, they say, are    10     (simple) not sufficient to explain the warming scene over the last century and a half.

【推荐2】In human history, many ancient and splendid civilizations were born and died. China is the only country     1     uninterrupted human civilization. Chinese civilization was born on the shores of the Yellow River. And the rich land     2     Chinese civilization began is Henan Province.

The Yellow River goes across     3     (center) Henan. It is China’s main north-to-south and east-to-west artery (干线). China’s most ancient tribal (部族的，种族的)     4     (lead), the Yellow Emperor and the Yan Emperor,    5     (bear) here. Even today, Chinese people all over the world still proudly call     6     (them) the descendants (后裔) of these two emperors.

The river     7     (hold) its unshakable position in the heart of every Chinese, respected by every generation and called “the Mother River”. With intelligence, hard work and determination, Chinese descendants pursue co-existence and common prosperity on this land. The 5,464-km-long Yellow River breaks the last barrier and flows into the broad plain,     8     (form) the cradle (摇篮) of Chinese civilization.

Till now, the Yellow River     9     (raise) 13 dynasties’ capital Luoyang, 8 dynasties’ capital Kaifeng and the biggest economic center in     10     (it) area—Zhengzhou.

The cave dwelling ( Yaodong in Chinese) in Xi’an , Shaanxi Province, is laid out in rows one atop the other, looking like buildings of multiple floors in the distance . It is a sort of distinctive cave house     1     (dig) into the mountains for dwelling of many laboring people on the Loess Plateau in northwest China.

A cave house is usually six meters deep and four meters wide. Stoneslabs (厚板)    2    (pile) up to form a semicircle at the entrance,     3     is decorated with beautiful wood or metal windows in a     4     (vary) of styles. The types of the cave dwelling can be divided into the earth cave dwelling , brick cave dwelling     5     stone dwelling. For centuries, they have been regarded     6    the symbol of the peasants in northern part of Shaanxi Province.

The beauty about the cave dwelling is     7    they help maintain local geography and save on farmlands by     8    (make) use of space that would have been otherwise left unused . They are warm in winter and cool in summer. The temperature inside is usually 13 degrees Celsius higher than in the open in winter and 10 degrees Celsius     9     (low) in summer. Statistics show that 40 million people live in cave dwellings that are scattered over an area of 600,000 square kilometers in     10     middle and upper reaches of the Yellow River.