In 1970 geologists Kenneth J. Hsu and William B.F. Ryan were collecting researchdatawhile aboard the oceanographic researchvesselGlomar Challenger. Anobjectiveof thisparticularcruisewas toinvestigatethe floor of theMediterraneanand toresolvequestions about its geologichistory. One question was related toevidencethat theinvertebratefauna(animals without spines) of theMediterraneanhad changedabruptlyabout 6 million years ago. Most of the older organisms were nearly wiped out, although a fewhardyspeciessurvived. A few managed tomigrateinto the Atlantic. Somewhatlater, the migrants returned, bringing newspecieswith them. Why did the nearextinctionand migrationsoccur?

Another task for the Glomar Challenger’s scientists was to try todeterminetheoriginof the domelike masses buried deepbeneaththeMediterraneanseafloor. These structures had been detected years earlier by echo-sounding instruments, but they had never been penetrated in thecourseof drilling. Were they salt domes such as arecommonalongthe United StatesGulfCoast, and if so, why should there have been so muchsolidcrystallinesaltbeneaththe floor of theMediterranean?

With question such as these clearly before them, the scientists aboard the Glomar Challenger processed to theMediterraneanto search for the answers. On August 23, 1970, they recovered asample. Thesampleconsisted of pebbles of hardenedsedimentthat had once beensoft, deep-sea mud, as well as granules of gypsum and fragments ofvolcanicrock. Not a singlepebblewas found that might have indicated that the pebbles came from the nearbycontinent. In the days following, samples ofsolidgypsum were repeatedly brought ondeckas drilling operations penetrated the seafloor. Furthermore, the gypsum was found topossesspeculiarities ofcompositionand structure that suggested it had formed ondesertflats. Sedimentabove and below the gypsumlayercontained tinymarinefossils, indicating open-ocean conditions. As they drilled into the central and deepest part of theMediterraneanbasin, the scientists tooksolid, shiny,crystallinesalt from thecorebarrel. Interbedded with the salt were thin layers of what appeared to be windblownsilt.

The time had come toformulateahypothesis. The investigators theorized that about 20 million years ago, theMediterraneanwas abroadseaway linked to the Atlantic by two narrow straits. Crustalmovements closed the straits, and the landlockedMediterraneanbegan toevaporate. Increasingsalinitycaused by theevaporationresulted in the extermination of scores ofinvertebratespecies. Only a few organisms especiallytolerantof very salty conditions remained. Asevaporationcontinued, theremainingbrine (salt water) became sodensethat thecalciumsulfate of the hardlayerwas precipitated. In the central deeper part of thebasin, the last of the brine evaporated toprecipitatemoresolublesodiumchloride (salt). Later, under the weight of overlying sediments, this salt flowed plastically upward to form salt domes. Before this happened, however, theMediterraneanwas avastdesert3,000 meters deep. Then, about 5.5 million years ago came the deluge. As a result ofcrustaladjustments and faulting, the Strait of Gibraltar, where theMediterraneannow connects to the Atlantic, opened, and water cascaded spectacularly back into theMediterranean. Turbulent waters tore into the hardened salt flats, broke them up, and ground them into the pebbles observed in the firstsampletaken by the Challenger. As thebasinwas refilled, normalmarineorganisms returned. Soonlayerofoceanicoozebegan toaccumulateabove the old hardlayer. The salt and gypsum, the faunal changes, and the unusualgravelprovidedabundantevidencethat theMediterraneanwas once adesert.

Questions:
question_stem: The word “objective” in the passage is closest in meaning to
choices: tag: A
text: achievement

tag: B
text: requirement

tag: C
text: purpose

tag: D
text: feature
answer_key: C
explanation: objective: 目标，目的。A 是成就；B 是要求；C 是目的；D 是特征。对应原文:An objective of this particular cruise was to investigate the floor of the Mediterranean and to resolve questions about its geologic history.意思为：这次特别巡航的一个目的是调查地中海的地层以及解决关于其地质历史的问题。则可得出答案 C。

question_stem: Which of the following is NOT mentioned in paragraph 1 as a change that occurred in the fauna of the Mediterranean?
choices: tag: A
text: Most invertebrate species disappeared during a wave of extinctions.

tag: B
text: A few hardy species wiped out many of the Mediterranean’s invertebrates.

tag: C
text: Some invertebrates migrated to Atlantic Ocean.

tag: D
text: New species of fauna populated the Mediterranean when the old migrants returned.
answer_key: B
explanation: EXCEPT 题，排除法。A 中的 inteverbrate 做关键词定位至第三句，但这句只说 change，下一句才对应 A 答案，所以 A 对，不选；注意原文说大部分 wiped out，一部分 hardy 的剩下了，而 B 说 hardy 的把大部分轰出去了，错，所以选 B；C 的 Atlantic 对应倒数第二句，对，不选；D 的 old migrants 对应最后一句，对，不选