托福阅读真题Official 43 Passage 1（二）

托福阅读真题Official 43 Passage 1（二）

Seagrasses

Many areas of the shallow sea bottom are covered with a lush growth of aquatic flowering plants adapted to live submerged in seawater.These plants are collectively called seagrasses.Seagrass beds are strongly influenced by several physical factors.The most significant is water motion:currents and waves.Since seagrass systems exist in both sheltered and relatively open areas,they are subject to differing amounts of water motion.For any given seagrass system,however,the water motion is relatively constant.Seagrass meadows in relatively turbulent waters tend to form a mosaic of individual mounds,whereas meadows in relatively calm waters tend to form flat,extensive carpets.The seagrass beds,in turn,dampen wave action,particularly if the blades reach the water surface.This damping effect can be significant to the point where just one meter into a seagrass bed the wave motion can be reduced to zero.Currents are also slowed as they move into the bed.

The slowing of wave action and currents means that seagrass beds tend to accumulate sediment.However,this is not universal and depends on the currents under which the bed exists.Seagrass beds under the influence of strong currents tend to have many of the lighter particles,including seagrass debris,moved out,whereas beds in weak current areas accumulate lighter detrital material.It is interesting that temperate seagrass beds accumulate sediments from sources outside the beds,whereas tropical seagrass beds derive most of their sediments from within.

Since most seagrass systems are depositional environments,they eventually accumulate organic material that leads to the creation of fine-grained sediments with a much higher organic content than that of the surrounding unvegetated areas.This accumulation,in turn,reduces the water movement and the oxygen supply.The high rate of metabolism(the processing of energy for survival)of the microorganisms in the sediments causes sediments to be anaerobic(without oxygen)below the first few millimeters.According to ecologist J.W.Kenworthy,anaerobic processes of the microorganisms in the sediment are an important mechanism for regenerating and recycling nutrients and carbon,ensuring the high rates of productivity—that is,the amount of organic material produced—that are measured in those beds.In contrast to other productivity in the ocean,which is confined to various species of algae and bacteria dependent on nutrient concentrations in the water column,seagrasses are rooted plants that absorb nutrients from the sediment or substrate.They are,therefore,capable of recycling nutrients into the ecosystem that would otherwise be trapped in the bottom and rendered unavailable.

Other physical factors that have an effect on seagrass beds include light,temperature,and desiccation(drying out).For example,water depth and turbidity(density of particles in the water)together or separately control the amount of light available to the plants and the depth to which the seagrasses may extend.Although marine botanist W.A.Setchell suggested early on that temperature was critical to the growth and reproduction of eelgrass,it has since been shown that this particularly widespread seagrass grows and reproduces at temperatures between 2 and 4 degrees Celsius in the Arctic and at temperatures up to 28 degrees Celsius on the northeastern coast of the United States.Still,extreme temperatures,in combination with other factors,may have dramatic detrimental effects.For example,in areas of the cold North Atlantic,ice may form in winter.Researchers Robertson and Mann note that when the ice begins to break up,the wind and tides may move the ice around,scouring the bottom and uprooting the eelgrass.In contrast,at the southern end of the eelgrass range,on the southeastern coast of the United States,temperatures over 30 degrees Celsius in summer cause excessive mortality.Seagrass beds also decline if they are subjected to too much exposure to the air.The effect of desiccation is often difficult to separate from the effect of temperature.Most seagrass beds seem tolerant of considerable changes in salinity(salt levels)and can be found in brackish(somewhat salty)waters as well as in full-strength seawater

Question 3 of 14

In paragraph 2,the author mentions the libraries at Antioch and Alexandria in order to

A.provide evidence that the library was a cultural institution in the East before it spread to the West

B.explain why it was important for Greek to become the great international language

C.identify two of the sources of Greek cultural influence within Alexander’s empire

D.support the claim that the Greeks transformed Middle Eastern garrisons and military posts into cultural centers

正确答案：C

题目详解

题型分类：修辞目的题

题干分析：这一句为举例，一般用于证明前一句观点。

选项分析：

C选项：根据libraries可以定位到第二段第三句，并可以得到libraries是很好的传播文化的途径，与C选项对应。

A选项：原文并没有提到，所以与原文无关。（原文有提到library提供证据证明图书馆在向西方传播之前是东方的一个文化机构，但是没有说到before it spread to the west，属于无中生有。）。

B选项：根据international language可以定位到第一句，但并没有提到重要性，所以B选项为无中生有。

D选项：可以定位到第三句话，但原文表示garrison和cultural centers为并列关系，二者是并存的，所以D选项与原文矛盾。

Question 4 of 14

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.

A.Assemblies were held in the agora to discuss some issues of the day,but more fundamental questions were decided by key individuals.

B.In a culture where philosophical discussions were frequent,some individuals questioned the value of a life focused on the marketplace.

C.Life centered around the agora,an open marketplace and site for public debate,where individuals could participate in decision making.

D.The focus of individuals was on fundamental topics such as the purpose of government and the connection between law and freedom.

正确答案：C

题目详解

题型分类：简化句子题

原文分析：考察识别主干内容和核心逻辑的能力（被简化句里的主干&逻辑）。注意原文的逻辑词as well as，所以原文的简化应为：The focus of life was the agora could be held and where issues of the day,as well as more fundamental topics,could be discussed and decisions made by individuals in person。

选项分析：

C选项，原文的中文意思：生活的焦点是可以举行集会，在那里可以讨论当天的问题，以及更基本的主题，并由个人亲自作出决定。所以C选项符合意思。

A选项意思为集会在集市上举行，讨论当时的一些问题，但更基本的问题由关键人物决定。这句话的逻辑不对，原文没有转折。

B选项意思为在一个哲学讨论频繁的文化中，一些人质疑专注于市场的生活的价值。这句话与原文提干无关。

D选项意思为个人的注意力集中在诸如政府的目的和法律与自由之间的联系等基本问题上。这句话与原文不符，逻辑不对。