请阅读Passage 1，完成1~5小题。 　　Passage 1 　　Today's adu

[单选题]请阅读Passage 1，完成1~5小题。 　　Passage 1 　　Today's adults grew up in schools designed to sort us into the various segments of our social and economic system.The amount of time available to learn was fixed: one year per grade.The amount learned by the end of that time was free to vary: some ofus leamed a great deal; some,very little.As we advanced through the grades,those who had learned a great deal in previous grades continued to build on those foundations.Those who had failed to master the early prerequisites within the allotted time failed to learn that which followed.After 12 or 13 years of cumulative treatment of this kinD.we were,in effect,spread along an achievement continuum that was ultimately reflected in each student's rank in class upon graduation. 　　From the very earliest grades,some students learned a great deal very quickly and consistently scored high on assessments.The emotional effect of this was to help them to see themselves as capable learners,and so these students became increasingly confident in school.That confidence gave them the inner emotional strength to take the risk of striving for more success because they believed that success was within their reach.Driven forward by this optimism,these students continued to try harD.and that effort continued to result in success for them.They became the academic and emotional winners.Notice that the trigger for their emotional strength and their learning success was their perception of their success on formal and informal assessments. 　　But there were other students who didn't fare so well.They scored very low on tests,beginning in the earliest grades.The emotional effect was to cause them to question their own capabilities as learners.They began to lose confidence,which,in turn,deprived them of the emotional reserves needed to continue to take risks.As their motivation warneD.of course,their performance plummeted.These students embarked on what they believed to be an irreversible slide toward inevitable failure and lost hope.Once again,the emotional trigger for their decision not to try was their perception of their performance on assessments. 　　Consider the reality-indeed.the paradox-of the schools in which we were reared.If some students worked hard and learned a lot,that was a positive result,and they would finish high in the rank order.But if some students gave up in hopeless failure,that was an acceptable result,too, because they would occupy places very low in the rank order.Their achievement results fed into the implicit mission of schools: the greater the spread of achievement among students,the more it reinforced the rank order.This is why,if some students gave up and stopped trying (even dropped out of school),that was regarded as the student's problem,not the teacher's or the school's. 　　Once again,please notice who is using test results to decide whether to strive for excellence or give up in hopelessness.The "data-based decision makers" in this process are students themselves.Students are deciding whether success is within or beyond reach,whether the learning is worth the required effort,and so whether to try or not.The critical emotions underpinning the decision making process include anxiety,fear of failure,uncertainty,and unwillingness to take risks-all triggered by students' perceptions of their own capabilities as reflected in assessment results. 　　Some students responded to the demands of such environments by working hard and learning a great deal.Others controlled their anxiety by giving up and not caring.The result for them is exactly the opposite of the one society wants.Instead of leaving no child behinD.these practices,in effect,drove down the achievement of at least as many students as they successfully elevated.And the evidence suggests that the downside victims are more frequently members of particular socioeconomic and ethnic minorities.

Which of the following is closest in meaning to the underlined word "plummeted" inParagraph 3?

A. Punished timely.
B. Spread widely.
C. Continued gradually.
D. Dropped sharply.