单选题Questions 18-20 are based on the following monologue introducing a nature tendency of plants. You now have 15 seconds to read Questions 18-20.

单选题Worldwide every day, we devour the energy equivalent of about 200 million barrels of oil. Most of the energy on earth comes from the sun. In fact enough energy from the sun hits the planet's surface each minute to cover our needs for an entire year, we just need to find an efficient way to use it. So far the energy in oil has been cheaper and easier to get at. But as supplies dwindle, this will change, and we will need to cure our addiction to oil. Burning wood satisfied most energy needs until the steam-driven industrial revolution, when energy-dense coal became the fuel of choice. Coal is still used, mostly in power stations, to cover one quarter of our energy needs, but its use has been declining since we started pumping up oil. Coal is the least efficient, unhealthiest and most environmentally damaging fossil fuel, but could make a comeback, as supplies are still plentiful; its reserves are five times larger than oil's. Today petroleum, a mineral oil obtained from below the surface of the Earth and used to produce petrol, diesel oil and various other chemical substances, provides around 40% of the world's energy needs, mostly fuelling automobiles. The US consumes a quarter of all oil, and generates a similar proportion of greenhouse gas emissions. The majority of oil comes from the Middle East, which has half of known reserves. But other significant sources include Russia, North America, Norway, Venezuela and the North Sea. Alaska's Arctic National Wildlife Refuge could be a major new US source, to reduce reliance on foreign imports. Most experts predict we will exhaust easily accessible reserves within 50 years, though opinions and estimates vary. We could fast reach an energy crisis in the next few decades, when demand exceeds supply. As conventional reserves become more difficult to access, others such as tar sands may be used instead. Petrol could also be obtained from coal. Since we started using fossil fuels ,we have released 400 billion tones of carbon, and burning the entire reserves could eventually raise world temperatures by 13℃. Among other horrors, this would result in the destruction of all rainforests and tile inching of all Arctic ice.

单选题In colonial America, where did coppersmiths usually obtain the material to make copper articles?

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单选题Du Bois was a sociological and educational pioneer who challenged the established system of education that tended to restrict rather than to advance the progress of black Americans. He challenged what is called the "Tuskegee machine" of Booker T. Washington, the leading educational spokesperson of the blacks in the US. A sociologist and historian, Du Bois called for a more determined and activist leadership than Washington provided. Unlike Washington, whose roots were the southern black agriculture, Du Bois's career spanned both sides of the Mason-Dixon Line. He was a native of Massachusetts, received his undergraduate education from Fisk University in Nashville, did his graduate study at Harvard University, and directed the Atlanta University Studies of Black American Life in the South. Du Bois approached the problem of racial relations in the United States from two dimensions: as a scholarly researcher and as an activist for civil rights. Among his works was the famous empirical sociological study, The Philadelphia Negro : A Social Study, in which he examined that city's black population and made recommendations for the school system. Du Bois's Philadelphia study was the pioneer work on urban blacks in America. Du Bois had a long and active career as a leader in the civil rights movement. He helped to organize the Niagara Movement in 1905, which led to the National Association for the Advancement of Colored People (NAACP), established in 1909. From 1910 until 1934, Du Bois edited The Crisis, the major journal of the NAACP. In terms of its educational policy, the NAACP position was that all American children and youth shouId have genuine equality of educational opportunity. This policy, which Du Bois helped to formulate, stressed the following themes: (1)public schooling should be free and compulsory for all American children; (2) secondary schooling should be provided for all youth; (3) higher education should not be monopolized by any special class or race. As a leader in education, Du Bois challenged not only the tradition of racial segregation in the schools but also the accornmodationist ideology of Booker T. Washington. The major difference between the two men was that Washington sought change that was evolutionary in nature and did not upset the social order, whereas Du Bois demanded immediate change. Du Bois believed in educated leadership for blacks, and he developed a concept referred to as the "talented tenth", according to which 10 percent of the black population would receive a traditional college education in preparation for leadership.

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单选题In the third paragraph, the phrase "on impulse" is closest in meaning to

单选题 Questions 14—16 are based on the following dialogue.

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单选题The female mosquito bites because

单选题The word "client" in "Washington's client states" in paragraph 3 was closest in meaning to which of the following word?

单选题Early in the age of affluence (富裕) that followed World War Ⅱ, an American retailing analyst named Victor Lebow proclaimed, "Our enormously productive economy...demands that we make consumption our way of life, that we convert the buying and use of goods into rituals, that we seek our spiritual satisfaction, our ego satisfaction, in consumption. We need things consumed, burned up, worn out, replaced and discarded at an ever increasing rate." Americans have responded to Lebow"s call, and much of the world has followed. Consumption has become a central pillar of life in industrial lands and is even embedded in social values. Opinion surveys in the world"s two largest economics-Japan and the United States-show consumerist definitions of success becoming ever more prevalent. Over consumption by the world"s fortunate is an environmental problem unmatched in severity by anything but perhaps population growth. Their surging exploitation of resources threatens to exhaust or unalterably spoil forests, soils, water, air and climate. Ironically, high consumption may be a mixed blessing in human terms, too. The time-honored values of integrity of character, good work, friendship, family and community have often been sacrificed in the rush to riches. Thus many in the industrial lands have a sense that their world of plenty is somehow hollow, that misled by a consumerist culture, they have been fruitlessly attempting to satisfy what are essentially social, psychological and spiritual needs with material things. Of course, the opposite of over consumption, poverty, is no solution to either environmental or human problems. It is infinitely worse for people and bad for the natural world too. Dispossessed (被剥夺得一无所有的) peasants slash, and burn their way into the rain forests of Latin America, and hungry nomads (游牧民族) turn their herds out onto fragile African grassland, reducing it to desert. If environmental destruction results when people have either too little or too much, we are left to wonder how much is enough. What level of consumption can the earth support? When dose having more cease to add noticeably to human satisfaction?