Spartina alterniflora, known as cordgrass, is adeciduous,perennialflowering plant native to the Atlanticcoastand theGulfCoastof the United States. It is thedominantnativespeciesof thelowersalt marshesalongthese coasts, where it grows in theintertidalzone(the area covered by water some parts of the day andexposedothers).

These natural salt marshes are among the mostproductivehabitats in themarineenvironment. Nutrient-rich water is brought to the wetlands during each hightide, making a highrateof food production possible. As the seaweed andmarshgrass leaves die,bacteriabreakdown the plantmaterial, and insects, small shrimplike organisms, fiddler crabs, andmarshsnails eat the decaying planttissue,digestit, and excrete wastes high in nutrients. Numerousinsectsoccupythemarsh, feeding on living or dead cordgrasstissue, and redwing blackbirds, sparrows, rodents, rabbits, and deer feed directly on the cordgrass. Eachtidalcyclecarries plantmaterialinto the offshore water to be used by the subtidal organisms.

Spartina is anexceedinglycompetitiveplant. It spreadsprimarilybyundergroundstems; colonies form when pieces of therootsystem or whole plantsfloatinto an area and takerootor when seedsfloatinto asuitablearea andgerminate. Spartina establishes itself on substrates ranging from sand andsilttograveland cobble and istolerantof salinities ranging from that of near freshwater (0.05 percent) to that of salt water (3.5 percent). Because theylackoxygen,marshsediments are high in sulfides that aretoxicto most plants. Spartina has theabilityto take up sulfides andconvertthem to sulfate, a form ofsulfurthat the plant can use; thisabilitymakes it easier for the grass tocolonizemarshenvironments. Anotheradaptiveadvantageis Spartina’sabilityto usecarbondioxidemore efficiently than most other plants.

These characteristics make Spartina avaluablecomponentof the estuaries where it occurs naturally. The plant functions as a stabilizer and asedimenttrapand as a nursery area for estuarine fish andshellfish. Once established, a stand of Spartina begins totrapsediment, changing thesubstrateelevation, andeventuallythe stand evolves into a highmarshsystem where Spartina isgraduallydisplaced by higher-elevation, brackish-waterspecies. Aselevationincreases, narrow, deep channels of water formthroughoutthemarsh. Alongthe eastcoastSpartina is consideredvaluablefor itsabilityto preventerosionand marshlanddeterioration; it is also used for coastalrestorationprojects and the creation of new wetland sites.

Spartina was transported to WashingtonStatein packing materials for oysters transplanted from the eastcoastin 1894. Leaving itsinsectpredators behind, the cordgrass has been spreading slowly and steadilyalongWashington’stidalestuaries on the westcoast, crowding out the native plants anddrasticallyaltering thelandscapeby trappingsediment. Spartina modifiestidalmudflats, turning them into high marshesinhospitableto the many fish andwaterfowlthatdependon the mudflats. It is already hampering theoysterharvestand the Dungenesscrabfishery, and it interferes with the recreational use of beaches and waterfronts. Spartina has been transplanted to England and to New Zealand for landreclamationand shorelinestabilization. In New Zealand the plant hasspreadrapidly, changing mudflats withmarshyfringes toextensivesalt meadows and reducing the number and kinds of birds and animals that use themarsh.

Efforts to control Spartina outside its natural environment have included burning, flooding, shading plants with blackcanvasorplastic, smothering the plants with dredged materials orclay, applyingherbicide, and mowing repeatedly. Little success has been reported in New Zealand and England; WashingtonState’smanagementprogram has tried many of these methods and is presently using theherbicideglyphosphate to control itsspread. Work has begun todeterminethefeasibilityof using insects as biological controls, buteffectivebiological controls are considered years away. Evenwith amassiveeffort, it is doubtful that complete eradication of Spartina from nonnative habitats is possible, for it has become anintegralpart of these shorelines and estuaries during the last 100 to 200 years.

Questions:
question_stem: According to paragraph 1, each of the following is true of Spartina alrerniflora EXCEPT:
choices: tag: A
text: It rarely flowers in salt marshes.

tag: B
text: It grows well in intertidal zones.

tag: C
text: It is commonly referred to as cordgrass.

tag: D
text: It occurs naturally along the Gulf Coast and the Atlantic coast of the United States.
answer_key: A
explanation: A EXCEPT 题，排除法。A 的 salt marshes 做关键词定位至第二句，但这句没说是否开花的信息，第一句说 spartina 是 perennial flowering plant，而 A 说不开花，所以 A 说反，选；B 的 intertidal zone 做关键词同样定位至第二句，正确，不选；C 的 cordgrass 做关键词定位至首句，说 spartina 也叫 cordgrass，正确，不选；D 的一系列专有名词做关键词定位至首句，正确，不选。此题 pps 的答案是错的，正确答案是 A。

question_stem: According to paragraph 2, a major reason why natural salt marshes are so productive is that they are
choices: tag: A
text: inhabited by long-lived seaweed and marsh grasses that reproduce gradually

tag: B
text: kept clear of excess plant material by the tides

tag: C
text: regularly supplied with high levels of nutrients

tag: D
text: home to a wide variety of different species of grasses
answer_key: C
explanation: C 以 salt marshes are so productive 做关键词定位至第二句，说 nutrient-rich 富营养的水被潮水带到 marsh，导致生产率很高，所以正确答案是 C。其他答案都没说。

question_stem: Which of the sentences below best express the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
choices: tag: A
text: Insects feed only on dead cordgrass, while most other marsh inhabitants feed on live cordgrass.

tag: B
text: The marsh is a good habitat for insects, but a relatively poor one for birds and animals.

tag: C
text: Although cordgrass provides food for birds and animals, it gives insects both food and a place to live.

tag: D
text: Cordgrass provides food for numerous insects, birds, and other animals.
answer_key: D
explanation: D 原文的结构是 insects 和一大堆乱七八糟的动物都吃 cordgrass，所以正确答案是 D。A 的 only dead cordgrass 与原文相反；B 的 habitat 和 C 的 a place to live 都没说。

question_stem: What is the organizational structure of paragraph 3?
choices: tag: A
text: It makes a general claim about Spartina and then provides specific evidence to defend that claim against objections to the claim.

tag: B
text: It presents a general characterization of Spartina and then describes particular features on which this characterization is based.

tag: C
text: It reports a widely held view about Spartina and then considers evidence both for and against that view.

tag: D
text: It presents a general hypothesis about Spartina and then lists specific evidence that disputes that hypothesis.
answer_key: B
explanation: B 问整段的结构，先看开头，再看第二句和最后一句。第一句说 S 是一个非常强的 competitive 植物，第二句说这种植物怎么生长的，最后一句说另外一个 adaptive 的优势是能够利用二氧化碳，整个都在说 spartina 到底是怎么长的，它的2个 competitive 的特性是什么，对应 B 选项的 features。这一段从来没说过反对，所以 A 的 objection，C 的 against 和 D 的 dispute 都不对。

question_stem: The word "exceedingly" in the passage is closest in meaning to
choices: tag: A
text: unusually

tag: B
text: dangerously

tag: C
text: surprisingly

tag: D
text: highly
answer_key: D
explanation: D exceedingly: 非常，极其。A 选项是异乎寻常的，B 选项是危险地，C 选项是惊人地，D 选项是非常，高度地。所以正确答案是 D 的 highly。

question_stem: According to paragraph 3, one reason that Spartina is able to compete in marsh environments so successfully is its ability to
choices: tag: A
text: alter the substrate in which it grows

tag: B
text: convert sulfides into a usable form of sulfur

tag: C
text: grow and produce seeds while floating on the surface of the water

tag: D
text: produce carbon dioxide with great efficiency
answer_key: B
explanation: B 以 marsh environments 做关键词定位至倒数第二句，说 spartina 能够吸收 sulfide 并将其转化为 sulfate，这一能力使 spartina 能够占领 marsh environments，所以正确答案是 B，A 的改变 substrate，C 的 floating on the surface 和 D 的 produce carbon dioxide 都没讲到。

question_stem: Paragraph 4 suggests that where Spartina occurs naturally, an established stand of it will eventually
choices: tag: A
text: create conditions in which it can no longer survive

tag: B
text: get washed away by water flowing through the deep channels that form around it

tag: C
text: become adapted to brackish water

tag: D
text: take over other grass species growing in the area
answer_key: A
explanation: A 以 established stand 做关键词定位至第三句，说一旦 establish 之后，spartina 会做 blabla 事情，stand 变成 high marsh system，spartina 会被替代，所以正确答案是 A 的 no longer survive。B 的 get washed，C 的 adapt 和 D 的 take over 都没说。

question_stem: According to paragraph 4, in its natural habitats, Spartina helps estuaries by
choices: tag: A
text: controlling marshland decline

tag: B
text: decreasing the substrate elevation

tag: C
text: reducing the brackishness of the water

tag: D
text: increasing the flow of water into the estuary
answer_key: A
explanation: A 整段都在说 spartina 如何帮忙 estuary 的，所以淡出从问题中找关键词不行，使用排除法。A 的 marshland 做关键词定位至最后一句，说 spartina 能阻止 erosion 和 marshland deterioration，与 A 的 decline 是同义替换，正确；B 的 substrate elevation，C 的 reduce brackishness 和 D 的 increase the flow of water 原文都没说。

question_stem: According to paragraph 5, Spartina negatively affects wildlife in estuaries by
choices: tag: A
text: trapping fish and waterfowl in sediment

tag: B
text: preventing oysters from transplanting successfully

tag: C
text: turning mudflats into high marshes and salt meadows

tag: D
text: expanding the marshy fringes of salt meadows
answer_key: C
explanation: C 由题干 negatively affects wildlife in estuaries 可从这样几句得到负面影响的信息：1 crowding out the native plants and drastically altering the landscape by trapping sediment. 2 Spartina modifies tidal mudflats, turning them into high marshes inhospitable to the many fish and waterfowl that depend on the mudflats. 3 changing mudflats with marshy fringes to extensive salt meadows and reducing the number and kinds of birds and animals that use the marsh. 正确答案 C

question_stem: The word "modifies" in the passage is closest in meaning to
choices: tag: A
text: creates

tag: B
text: changes

tag: C
text: grows on

tag: D
text: breaks down
answer_key: B
explanation: B  modify 改变，所以正确答案是 b。原文说 spartina 怎么样了 tidal mudflats，把它们变成 high marshes，turning into 是对前文 modify 的解释，所以正确答案是 change。a 创造 c 生长和 d 打破完全不靠谱

question_stem: According to paragraph 6, each of the following methods has been used in attempts to control Spartina EXCEPT
choices: tag: A
text: flooding plants

tag: B
text: cutting plants down repeatedly

tag: C
text: applying herbicides

tag: D
text: introducing predatory insects
answer_key: D
explanation: 题目问为了控制米草生长而采取的措施中未提及哪一个，对应原文句：
Efforts to control Spartina outside its natural environment have included burning, flooding, shading plants with black canvas or plastic, smothering the plants with dredged materials or clay, applying herbicide, and mowing repeatedly. 其中 flooding, applying herbicide, mowing repeatedly 分别为 ABC 选项含义，所以选 D。

question_stem: The word "Efforts" in the passage is closest in meaning to
choices: tag: A
text: Laws

tag: B
text: Suggestions

tag: C
text: Attempts

tag: D
text: Failures
answer_key: C
explanation: effort 努力，尝试，所以 c 的 attempt 正确。原文说控制 spartina 的什么包括烧，水淹，砍，闷死等等，law 和 suggestion 明显不对，因为已经付诸行动了，failure 失败与后文的 little success 重复，不选