[外语类试卷]大学英语四级模拟试卷459及答案与解析.doc
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1、大学英语四级模拟试卷 459及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed thirty minutes to write a composition on the topic: Will Computers Replace Us? You should write at least 120 words following the outline given in Chinese: 1. 电脑技术 迅猛发展,大有将人类取而代之之势; 2. 提出你自己的观点; 3. 讲述自己的理由。 Will Comp
2、uters Replace Us? 二、 Part II Reading Comprehension (Skimming and Scanning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-7, mark: Y (for YES) if the statement agrees with the informatio
3、n given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Diamonds are just carbon in its most concentrated form, the element that makes up 18 percent of the weight of your body. There is
4、 no other gemstone as cherished as the diamond, but in truth, diamonds are no rarer than many other precious gems. They continue to demand higher market prices because the majority of the diamond market is controlled by a single entity. The Origin of Diamonds Carbon is one of the most common element
5、s in the world, and is one of the four essentials for the existence of life. Humans are more than 18-percent carbon. When occurring in nature, carbon exists in three basic forms, of which diamond is an extremely hard, clear crystal. Diamonds form about 161 km below the Earths surface, in the molten
6、rock of the Earths mantle, which provides the right amounts of pressure and heat to transform carbon into a diamond. In order for a diamond to be created, carbon must be placed under at least 435,113 pounds per square inch (psi) of pressure at a temperature of at least 400 Celsius. If conditions dro
7、p below either of these two points, graphite will be created. At depths of 150 km or more, pressure builds to about 725,189 psi and heat can exceed 1,200 C. Kimberlite Pipes Most diamonds that we see today were formed millions (if not billions) of years ago. Powerful magma eruptions brought the diam
8、onds to the surface, creating kimberlite pipes. Kimberlite is named after Kimberly, South Africa, where these pipes were first found. Most of these eruptions occurred between 1,100 million and 20 million years ago. Kimberlite pipes are created as magma (岩浆 ) flows through deep fractures in the Earth
9、. The magma inside the kimberlite pipes acts like an elevator, pushing the diamonds and other rocks and minerals through the mantle and crust in just a few hours. These eruptions were short, but many times more powerful than volcanic eruptions that happen today. The magma eventually cooled inside th
10、ese kimberlite pipes, leaving behind conical veins of kimberlite rock that contain diamonds. Kimberlite is a bluish rock that diamond miners look for when seeking out new diamond deposits. The surface area of diamond-bearing kimberlite pipes ranges from 2 to 146 hectares. Diamonds may also be found
11、in river beds, which are called alluvial diamond sites. These are diamonds that originate in kimberlite pipes, but get moved by geological activity. Glaciers and water can also move diamonds thousands of miles from their original location. Cutting Diamonds There are special techniques that are used
12、to cut and shape a diamond before it gets to the jewelry store. Diamond cutters first try to remove any impurities or irregularities in the diamond. Sometimes, diamonds have to be sawed with the use of a phosphor-bronze blade or laser. Then the diamond is rubbed by another diamond to create facets-t
13、iny flat spots on the surface. Finally, the diamond is pressed against a rotating polishing wheel to give the diamond its finished look. Rating Diamonds Diamonds are judged on several factors that determine their beauty. Most diamonds never reach the consumer market because they are too flawed. Ofte
14、n, these diamonds are used for industrial purposes-as an abrasive, for drill bits or for cutting diamonds and other gems. If youve ever purchased a diamond, youve heard of the “4 Cs:“ 1. Cut-This refers to how the diamond has been cut and its geometric proportions. When a diamond is cut, facets are
15、created and the diamonds finished shape is determined. 2. Clarity-This is the measurement of a diamonds flaws, or inclusions that are seen in the diamond. 3. Carat-This is the weight of a diamond. One carat is equal to about 200 milligrams. 4. Color-In referring to transparent diamonds, the color sc
16、ale runs from D to Z, beginning with Icy White- the color of the most expensive diamonds-and ending with a light yellow. Other unique qualities of the diamond include its transparency, luster and dispersion of light. A diamond that is created from 100-percent carbon will be completely transparent. D
17、iamonds often contain other elements that can affect the color. Although we often think of diamonds as being clear, there are also blue, red, black, pale green, pink and violet diamonds. These colored diamonds are the truly rare ones. Marketing Diamonds Prior to the 1930s, diamond rings were rarely
18、given as engagement rings. Opals, rubies, sapphires and turquoise were deemed much more exotic gems to give as tokens of ones love. This idea of connecting diamonds to romance was captured in a brilliant ad campaign begun in the 1940s, causing demand for diamonds to increase. Surely youve heard the
19、De Beers advertisement telling you that “A Diamond Is Forever.“ This ad campaign, which was created by the N.W. Ayer advertising agency in 1947, changed the diamond market. In 2000, Advertising Age magazine named the ad campaign the slogan of the 20th century. Later ads by De Beers told consumers to
20、 hold onto their familys diamond jewelry and to cherish them as a family possession-and it worked. This eliminated the aftermarket for diamonds, which further enabled De Beers to control the market. Without people selling their diamonds back to jewelers or to other people, the demand for new diamond
21、s increased. There are fewer than 200 people or companies authorized to buy rough diamonds from De Beers. These people are called sightholders, and they purchase the diamonds through the Central Selling Organization (CSO), a subsidiary of De Beers that markets about 70 percent to 80 percent of the w
22、orlds diamonds. De Beers sells a parcel of rough diamonds to a sightholder, who in turn sends the diamonds to cutting facilities and then to distributors. There are rough diamonds sold outside the CSO. However, the cost of these diamonds is still largely influenced by the prices set by the CSO. Diam
23、onds are the most coveted of all precious gems, as is witnessed by the extremely high demand for them. While this has not always been the case, diamonds are nonetheless exquisite gems that go through a long, tedious refining process from the time they are pulled from the ground to when you see them
24、in the jewelry store. And, while some of the mystique of diamonds may be gone-theyre just carbon, after all-the diamond will likely continue to be a highly coveted jewel, because, well, “A Diamond Is Forever.“ 2 Carbon makes up about 1/4 of the human body. ( A) Y ( B) N ( C) NG 3 According to the pa
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