Passage Thirty-five (Exploration on the Origin of Continents)
　　The origin of continental nuclei has long been a puzzle. Theories advanced so far have generally failed to explain the first step in continent growth, or have been subject to serious objections. It is the purpose of this article to examine the possible role of the impact of large meteorites or asteroids in the production of continental nuclei. Unfortunately, the geological evolution of the Earth’s surface has had an obliterating effect on the original composition and structure of the continents to such an extent that further terrestrial investigations have small chance of arriving at an unambiguous answer to the question of continental origin. Paradoxically, clues to the origin and early history of the surface features of the Earth may be found on the Moon and planets, rather than on the Earth, because some of these bodies appear to have had a much less active geological history. As a result, relatively primitive surface features are preserved for study and analysis. In the case of both the Moon and Mars, it is generally concluded from the appearance of their heavily cratered surfaces that they have been subjected to bombardment by large meteoroids during their geological history. Likewise, it would appear a reasonable hypothesis that the Earth has also been subjected to meteoroid bombardment in the past, and that very large bodies struck the Earth early in its geological history.
　　The large crater on the Moon listed by Baldwin has a diameter of 285 km. However, if we accept the hypotheses of formation of some of the mare basins by impact, the maximum lunar impact crater diameter is probably as large as 650km. Based on a lunar analogy, one might expect several impact craters of at least 500km diameter to have been formed on Earth. By applying Baldwin’s equation, the depth of such a crater should be about 20km. Baldwin admits that his equation gives excessive depths for large craters so that the actual depth should be somewhat smaller. Based on the measured depth of smaller lunar crater. Baldwin’s equation gives the depth of the zone of brecciation for such a crater as about 75km. The plasticity of the Earth’s mantle at the depth makes it impossible to speak of “bracciation” in the usual sense. However, local stresses may be temporarily sustained at that depth, as shown by the existence of deep-focus earthquakes. Thus, short-term effects might be expected to a depth of more than 50km in the mantle.
　　Even without knowing the precise effects, there is little doubt that the formation of a 500-km crater would be a major geological event. Numerous authors have considered the geological implications of such an event. Donn et al. have, for example, called on the impact of continent-size bodies of sialic composition to from the original continents. Two major difficulties inherent in this concept are the lack of any known sialic meteorites, and the high probability that the energy of impact would result in a wide dissemination of sialic material, rather than its concentration at the point of impact.
　　Gilvarry, on the other hand, called on meteoroid impact to explain the production of ocean basins. The major difficulties with this model are that the morphology of most of the ocean basins is not consistent with impact, and that the origin and growth of continents is not adequately explained.
　　We agree with Donn at al. that the impact of large meteorites or asteroids may have caused continent formation, but would rather think in terms of the localized addition of energy to the system, rather than in terms of the addition of actual sialic material.
　　1.    A mare basin is
　　[A]. a formula for determining the relationship between the depth and width of craters.
　　[B]. a valley that is filled in when a spatial body has impact with the moon or the earth.
　　[C]. a planetoid (small planet) created when a meteorite, upon striking the moon, breaks off a part of the moon.
　　[D]. a dark spot on the moon, once supposed to be a sea, now a plain.
　　2.    The writer does not believe that
　　[A]. an asteroid is larger than a meteorite.
　　[B]. material from space, upon hitting the earth, was eventually distributed.
　　[C]. the earth, at one time, had craters.
　　[D]. ocean were formerly craters.
　　3.    The article is primarily concerned with
　　[A]. the origin of continents.
　　[B]. the relationship between astral phenomena and the moon.
　　[C]. differences of opinion among authoritative geologists.
　　[D]. the relationship between asteroids and meteorites.
　　4.    Sialic material refers to
　　[A]. the broken rock resulting from the impact of a meteorite against the earth.
　　[B]. material that exists on planets other than the earth.
　　[C]. a composite of rock typical of continental areas of the earth.
　　[D. material that is man-made to simulate materials that existed far back in geological history.

　　Vocabulary
　　1.    relentlessly 始终不2.    懈的
　　3.    obsolete 过时的，4.    大量的，5.    绝大部分的
　　6.    chunk 大块，7.    大量的，8.    绝大部分
　　9.    abysmal 无底的，10.    极端的
　　11.    Proteus 希12.    腊神话中海神，13.    能随意变化。这里指14.    flexible, 灵活多变
　　15.    take on 显现，16.    显示
　　17.    LOGO=logotyre 标18.    识语，19.    作为标20.    志的语言
　　21.    rapidly shifting 瞬息万22.    变的
　　23.    romanticizing 使浪漫化，24.    使幻想化
　　2.    In terms of drill and practice, self-paced computer-assisted instruction enables the student to advance rapidly-without being limited by the conflicting needs of the entire class.
　　[结构简析] 句子结构为主谓宾补，前后各用一个介词（短语），前in term of , 后without
　　[参考译文] 就练习和实践来讲，借助自行规定速度的计算机辅助的指令使学生突飞猛进而不受全班互相矛盾的需要所限制。
　　3.    Without romanticizing the machine, it is clear that computers uniquely change the potential for equipping today’s citizens for unprecedented tasks of the future.
　　[结构简析] 逻辑主语句。句前有一状语成分，without +分词+名词的句型。
　　[参考译文] 不必用浪漫主义的手法来形容计算机，我们可清楚看到，它是独一无二的改变今天公民的潜力，使他们能承担未来的史无前例的任务。
　　写作方法与文章大意
　　文章论述了“计算机的重要性”，采用一般到具体写作手法。一开始就提出：‘作为经济上先进而又脆弱的公民，必须始终不懈地提高技术素质，否则生活水平就会下降。因为未来国际竞争取决于技术，一切部门必须迎合这一要求。具体到工业和学校必须使用计算机。重点在学校，因为它是培训新人才的基地。所以三，四，五，七段涉及计算机在学校的种种功能。最后的结论：人才和计算机是决定性因素。
　　答案祥解
　　1.    B. 工艺技术。这在第一段就讲到“在未来，2.    国与国之间的竞争越来越以工艺技术为基础。尽管石油和其他自然资源仍很重要，3.    但它们不4.    会再对一个国家的经济实力起决定性的作用。”
　　A. 石油。 C. 自然资源，这两项不是决定性因素。 D. 教育。文内教育作为改革的一个方面，其重点是在学校内应用计算机，来改变教学质量，达到革新人才的目的。并不是直接参与竞争。可参看第2题的答案及译注。
　　5.    B. 计算机的重要性。整篇文章都显示了这一点。第三段“工业上，6.    信息处理和制定必要的改革计划以适应市场需要意味着越来越多使用计算机。学校紧跟工业之后……”第四段“计算机是一种变化多端，7.    神通广大的机器，8.    因为它显示千种图象，9.    发挥千种功能。而 10.    它的真正的革命性可在其相互作用的潜能中看出。有了先进的计算机，11.    学习可以个别进行，12.    速度自行规定。教师变得更有成效……。”第五段“……由于利用计算机，13.    在学校低年级就能教授物理学和高等数学概念……。”最后一段画龙点睛地指14.    出： “计算机独一无二地改变着那种今天公民能担当未来空前任务的潜能……新的竞争对手正在崛起，15.    自由的经济布局提出挑战。我们如何才能顺利的应战，16.    取决于我们对人的投资的多寡，17.    取决于我们怎么聪慧地应用新技术的学习工具。”所以
　　A. 计算机知识。 C. 知识的功能。 D. 技术功能，这三项只是计算机重要性中涉及到的一个方面，不能作为中心思想。
　　18.    D. 因为我们知道的一切19.    变得陈旧。第二段头几句话“我们决不20.    能吃老本，21.    当今的竞争使我们的大部分知识变得陈旧， 22.    非加以革新不23.    可。对每个人来说，24.    他们将惯常从事某几种职业，25.    并且非继续学习进修和从新接受训练不26.    可……。”都说明进修学习的原因。
　　A. 人们要做更多工作。文内没有提到。 B. 人们要到达非同一般的教育水平。这是目的，不是原因。 C. 人们不能吃老本。这话并没有完全讲清楚全部原因。
　　27.    A. 灵活多变。 Proteus 一词，28.    原义是指希29.    腊神话中变幻无常的海神，30.    普罗狄斯，31.    他可以随心所欲边成各种形状。这里指32.    灵活多变。