四级难度 Directions: In this section, there is a passage with ten blanks. You are required to select one word for each blank from a list of choices given in a word bank following the passage. Read the passage through carefully before making your choices. You may not use any of the words in the bank more than once. Questions 47 to 56 are based on the following passage. Under the influence of the global warming, temperatures in some regions rose several degrees in less than a century. Sea levels shot up nearly 400 feet, 47 coastal settlements and forcing people to 48 inland. Deserts spread throughout the world as vegetation shifted drastically in North America, Europe and Asia. After driving many of the animals around them to near extinction, people were forced to 49 their old way of life for a radically new survival strategy that resulted in widespread starvation and disease. The adaptation was farming, the global-warming crisis that 50 it happened more than 10,000 years ago. As environmentalists meet in Rio de Janeiro to ponder the global climate of the future earth, scientists are in the midst of a revolution in understanding how climate has changed in the past ----- and how those changes have transformed human 51 . Researchers have begun to 52 an illuminating picture of the powerful geological and astronomical forces that have combined to change the planet’s environment from hot to cold, wet to dry and back again over a time period stretching back hundreds of millions of years. Most important scientists are beginning to realize that the climatic changes have had a major 53 on the evolution of the human species. New research now suggests that climate shifts have played a key role in nearly every significant 54 point in human evolution, from the dawn of primates ( 灵长类动物 ) some 65 million years ago to human ancestors rising up to walk on two legs from the huge expansion of the human brain to the rise of agriculture. Indeed the human history has not been 55 touched by global climate change; some scientists argue it has in some instances been 56 by it. A) turning B) abandon C) leaving D) appearance E) rise up F) migrate G) driven H) changing I) gave rise to J) impact K) existence L) flooding M) piece together N) merely O) motivated