托福閱讀真題Official 43 Passage 1（二）

托福閱讀真題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

正確答案：C

題目詳解

題型分類：修辭目的題

題幹分析：這一句為舉例，一般用於證明前一句觀點。

選項分析：

C選項：根據libraries可以定位到第二段第三句，並可以得到libraries是很好的傳播文化的途徑，與C選項對應。

A選項：原文並沒有提到，所以與原文無關。（原文有提到library提供證據證明圖書館在向西方傳播之前是東方的一個文化機構，但是沒有說到before it spread to the west，屬於無中生有。）。

B選項：根據international language可以定位到第一句，但並沒有提到重要性，所以B選項為無中生有。

D選項：可以定位到第三句話，但原文表示garrison和cultural centers為並列關係，二者是並存的，所以D選項與原文矛盾。

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.

正確答案：C

題目詳解

題型分類：簡化句子題

原文分析：考察識別主幹內容和核心邏輯的能力（被簡化句裏的主幹&邏輯）。注意原文的邏輯詞as well as，所以原文的簡化應為：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。

選項分析：

C選項，原文的中文意思：生活的焦點是可以舉行集會，在那裏可以討論當天的問題，以及更基本的主題，並由個人親自作出決定。所以C選項符合意思。

A選項意思為集會在集市上舉行，討論當時的一些問題，但更基本的問題由關鍵人物決定。這句話的邏輯不對，原文沒有轉折。

B選項意思為在一個哲學討論頻繁的文化中，一些人質疑專注於市場的生活的價值。這句話與原文提幹無關。

D選項意思為個人的注意力集中在諸如政府的目的和法律與自由之間的聯係等基本問題上。這句話與原文不符，邏輯不對。

>> 雅思 托福 免費測試、量身規劃、讓英語學習不再困難<<