[外语类试卷]大学英语六级模拟试卷313及答案与解析.doc
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1、大学英语六级模拟试卷 313及答案与解析 一、 Part I Writing (30 minutes) 1 Directions: For this part, you are allowed 30 minutes to write a composition on the topic An Invitation Letter. You should write at least 150 words following the outline given below in Chinese: 1. 请你以大学校长的名义给校友们写一封 100周年校庆的邀请信,指出邀请的时间 2. 简单介绍学校 3
2、. 告诉对方联系方式,表示期待 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 1-4, mark: Y (for YES) if the statement agrees with the information
3、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 Trees To many, the word trees evokes images of such ancient, powerful, and majestic structures as the redwood and the giant sequoia
4、 (红杉 ), among the most massive and longest living organisms in the world. Although the majority of the Earths biomass is represented by trees, the fundamental importance of these seemingly ubiquitous plants for the very existence and diversity of life on Earth is perhaps not fully appreciated. Our v
5、ery biosphere is dependent on the metabolism, death, and recycling of plants, especially trees. Their vast trunks and root systems store carbon dioxide and water and respire oxygen into the atmosphere. The organic matter of the soil develops primarily from plant residues (that is, from decayed leave
6、s, twigs, branches, roots, and fallen trees), which release important nutrients, such as nitrogen, carbon, and oxygen. The tree is not an immutable biological category but rather a human concept based on visual criteria. Perhaps a general definition would describe a tree as a perennial(多年生的 ) woody
7、plant that develops along a single main trunk to a height of at least 4.5 metres at maturity. This may be contrasted with a shrub, which might be loosely defined as a woody plant with multiple stems; in most cases, a shrub is less than 3 metres tall. However, a species fitting the description of eit
8、her in one area of the world might not necessarily do so in other regions, since a variety of stresses shape the habit of the mature plant. Thus, a given woody species may be a tree in one set of habitats within its range and a shrub elsewhere. For example, the spruce and fir may thrive in the tree
9、form at the base of a mountain but assume a shrub form near the mountain-top, the variation due principally to stresses exerted by such environmental conditions as altitude, temperature, and oxygen tension. In the early stages of the development of terrestrial life, land plants were rootless and lea
10、fless, since they had their origins in aqueous environments, they did not require the specialized conducting and supporting tissues afforded by roots and stems, nor did they require localized regions of carbohydrate synthesis, since each cell was involved in metabolism, water and nutrient absorption
11、, and respiration. Habitats farther from the water as well as aerial habitats represented available uninhabited environments. One key to exploiting these habitats is large size. This, however, requires physiological and morphological (形态的 ) complexity. If all the tissues of massive tree trucks were
12、alive, for example, the physiological cost of maintaining these structures in the living state would be enormous, and probably unattainable. The elegant solution came in the form of tremendous structural adaptations, new tissues and organs permitted localization of the functions of the plant body. T
13、he evolution of vascular tissues and localized regions of cell division permitted the strengthening and conducting tissue, called wood, to be dead, hollow, thick-walled tubes at functional maturity. Roots provided anchorage and absorption of sufficient amounts of water and nutrients to support the h
14、uge biomass of the tree. Stems were not only strong enough to support the tree and project it into ever higher habitats but conductive enough to transport the water and nutrients to the leaves at the very top of the tree. The shape of a tree is an ecological construct as well, since its form is depe
15、ndent on the habitat and the stresses of the environment. Open-grown trees, such as those in gardens and parks, generally have foliage extending along the length of the trunk for a considerable distance. Forest trees, on the other hand, compete for growing space and generally have an expanse of foli
16、age-free bole below a more limited tree crown. The aggregate of the tree crowns constitutes the canopy of the forest, and this may be displayed in a single layer or stratified (分层 ) into several layers, depending on the number and kinds of trees that make up the forest. Forests are of immense import
17、ance in soil stabilization and erosion control, especially in mountainous and hilly regions; they also protect and conserve water supplies and prevent floods. Small groups of trees and even single trees have a similar role locally in preventing washouts and in holding stream banks. As mentioned abov
18、e, trees contribute significantly to nutrient recycling, carbon dioxide absorption, and oxygen generation. Carbonized and fossilized wood (coal) supplies fuel for energy needs; other fossilized products of trees include amber, which is formed from the gum of pines, and kauri gum (贝壳杉树胶 ). From earli
19、est times wood has been employed for such purpose as homes, rafts, canoes, fuel, and weapons. Primitive people were dependent on trees for many materials in addition to wood. Fruits and nuts of many kinds were important foods for both humans and animals. Leaves of palms and other trees were used for
20、 thatching roofs. Tapa cloth (构树皮布 ) and woven fabrics made from bark, leaves, and other tree parts were used for clothing. Utensils were fashioned from calabashes, coconuts, and other fruits. Medicines, including quinine, were obtained from trees, as were dyes, tanning materials, and spices. Modern
21、 civilizations are no less dependent on trees. Although substitutes now are commonly used for some tree products, the demand for trees remains strong, as in the manufacture of newsprint and other papers as well as cardboard and similar packagings. The plywood industry converts immense numbers of tre
22、es into building materials. Many tree products other than wood and its derivatives are important. Edible fruits produced by trees include apples, cherries, peaches, pears, and others in temperate climates; figs, persimmons, and citrus fruits (柑橘果 ) in warm-temperate and subtropical regions; breadfru
23、it, coconuts, jackfruit, and mangoes in tropical regions; and the important fruit of desert regions the date. The coconut, the oil plam, and the olive are important sources of oils and fats used as food and for other purposes. From trees come such spices as cinnamon (桂皮 ) and nutmeg; substances used
24、 in beverages, such as chocolate, coffee, and kola nuts; and chicle, the basis of chewing gum. It is true, however, that the history of civilization also includes incidences of waste, sometimes bordering on elimination of a species from a particular region. Great forests of cedars of Lebanon, for ex
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- 外语类 试卷 大学 英语六级 模拟 313 答案 解析 DOC
