11. According to paragraph 6, the composition of chondritic meteorites differs from the composition of the Sun primarily in
O containing nebular matter
O containing many fewer atoms of iron
O the relative amount of volatile elements
O the ratio of iron to silicon
细节题
定位词：composition of chondritic meteorites，differs from，the composition of the Sun
解析：The compositional similarity is striking. The major difference is that Allende is depleted in the most volatile elements, like hydrogen, carbon, oxygen, nitrogen, and the noble gases, relative to the Sun.选3
12. According to paragraph 6, what is the significance of the similarity in composition between chondrites and the Sun?
O It indicates what the matter from which planets were formed was probably like.
O It may explain howthe Sun originally developed.
O It helps scientists estimate the variations in the chemical composition of different meteors.
O It suggests that most meteorites may contain large quantities of volatile elements.
修饰目的题
定位词：similarity in composition between chondrites and the Sun
解析：Since practically all the solar system's mass resides in the Sun, this similarity in chemistry means that chondrites have average solar system composition, except for the most volatile elements; they are truly lumps of nebular matter, probably similar in composition to the matter from which planets were assembled.选1
Equally perplexing constituents of Allende are the refractory inclusions: irregular white masses that tend to be larger than chondrules. ■ They are composed of minerals uncommon on Earth, all rich in calcium, aluminum, and titanium, the most refractory (resistant to melting) of the major elements in the nebula. ■ The same minerals that occur in refractory inclusions are believed to be the earliest-formed substances to have condensed out of the solar nebula. ■ However, studies of the textures of inclusions reveal that the order in which the minerals appeared in the inclusions varies from inclusion to inclusion, and often does not match the theoretical condensation sequence for those metals. ■
13. Look at the four squares [■] that indicate where the following sentence could be added to the passage
It is therefore still unclear if all inclusions were formed in the same way.
Where would the sentence best fit?
插入题
解析：It is therefore still unclear if all inclusions were formed in the same way.
Equally perplexing constituents of Allende are the refractory inclusions: irregular white masses that tend to be larger than chondrules. ■ They are composed of minerals uncommon on Earth, all rich in calcium, aluminum, and titanium, the most refractory (resistant to melting) of the major elements in the nebula. ■ The same minerals that occur in refractory inclusions are believed to be the earliest-formed substances to have condensed out of the solar nebula. ■ However, studies of the textures of inclusions reveal that the order in which the minerals appeared in the inclusions varies from inclusion to inclusion, and often does not match the theoretical condensation sequence for those metals. ■
第四个选项之前提到inclusion不符合理论上金属浓缩顺序，所以之后应该放插入句，因为之前有研究否定，因而对内含物是否以同样的方式形成不确定，另外一个重要点是therefore，表示对前面的理论或者证明的承接，选4
14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Studies of the Allende meteorite provided information about the composition of chondritic meteorites and their possible origin.
O
O
O
Answer Choices
O When Allende entered Earth's atmosphere, it broke into thousands of pieces called chondrites because they look like glassy, black seeds.
O The mineral content of chondrules suggests that they were probably formed in isolated regions of the nebula that remained much hotter than the rest.
O Chondrules are tiny, millimeter-sized drops of silicate materials that probably formed when lumps of nebular dust were fused at extremely high temperatures and then quickly cooled.
O Irregularly shaped inclusions in Allende are composed of minerals that are resistant to melting and are believed to be the earlest minerals to have condensed out of the nebula.
O The matrix that holds the chondrules and inclusions together in Allende consists mainly of grains of nebular dust that were trapped inside the meteor before they could be melted.
O Except for being depleted in volatile elements, chondritic meteorites are probably very similar in composition to the matter from which planets were assembled.
总结题
解析：Studies of the Allende meteorite provided information about the composition of chondritic meteorites and their possible origin.两个信息，1是C陨石，2是起源
O When Allende entered Earth's atmosphere, it broke into thousands of pieces called chondrites because they look like glassy, black seeds.太过细节，名字的来源，跟起源无关，成分无关
O The mineral content of chondrules suggests that they were probably formed in isolated regions of the nebula that remained much hotter than the rest.即提到C陨石，又说到起源，来自星云
O Chondrules are tiny, millimeter-sized drops of silicate materials that probably formed when lumps of nebular dust were fused at extremely high temperatures and then quickly cooled.
O Irregularly shaped inclusions in Allende are composed of minerals that are resistant to melting and are believed to be the earlest minerals to have condensed out of the nebula.inclusion跟主体无关
O The matrix that holds the chondrules and inclusions together in Allende consists mainly of grains of nebular dust that were trapped inside the meteor before they could be melted.
O Except for being depleted in volatile elements, chondritic meteorites are probably very similar in composition to the matter from which planets were assembled.第六段观点，即提到C陨石，又说到它们的起源从planet而来
参考答案：
1-5：DCBDB 6-10:BDAAB 11-13:CAD
14. The mineral content ...
The matrix that ...
Except for being ...
参考译文：
阿伦德陨星
在 1969年2月8日子夜后的某一时刻，一颗巨大的闪亮流星划破了地球的大气层，碎成无数的碎块坠落到地面，散布在墨西哥奇瓦瓦州境内长50英里宽10英里 的区域内。这次坠落为人们发现的第一块陨石是位于皮柏里托•德•阿伦德村。总共大约找到了2吨的陨星碎片，所有的碎片都是以首次发现的所在地阿伦德命名。
每 块阿伦德样本都覆盖着黑色的、玻璃样的熔壳，这层熔壳是在它们的外表面与地球大气层摩擦减速中熔化形成的。把阿伦德陨石破开发现里面含有各种各样细小的、 与众不同的物体，这些物体球状或者不规则，嵌在深灰色的基质（结合物质）中，它们曾是太阳星云——形成我们的太阳系的由气体和尘埃组成的星级云团一部分。
阿 伦德陨星属于球粒陨石。球粒陨石的名字是源于希腊语中的单词“chondros”，意思是种子，这是指它们的外观看起来仿佛是岩石中镶嵌着细小的种子。这 些种子实际上是陨石球粒：毫米级的熔融硅酸盐物质小液滴冷却而成的玻璃球和水晶球。少数陨石球粒含有未遭熔化的颗粒，所以这些神秘的陨石球粒肯定是在接近 1700摄氏度的高温下熔化的星云尘埃致密团块中形成的，随后再这些团块在幸存的颗粒尚未熔化之前就冷却了。对陨石球粒质地的研究确认它们的确是以极快的 速度冷却的，短则几分钟，长则数小时，所以形成陨石球粒的高温事件肯定是限于局部的。看起来极不可能是星云的大部分遭遇了如此极端的高温，大部分区域不可 能很快的散热。陨石球粒肯定是在星云内部能够快速散热的小型袋状结构处被熔化的。这些奇特的玻璃球目前仍是未解之谜。
同样令人困惑的是阿伦 德陨星的成分是耐高温的内含物：比陨石球粒要大些的不规则的白色团块。它们是由地球上罕见的矿物质组成的，富含钙、铝以及在星云中最耐高温的（耐熔化的） 主要元素钛。这些出现在耐高温内含物中的矿物质被认为是在太阳星云中最早凝结而成的物质。 然而，对内含物质地的研究发现不同的内含物中矿物质出现的顺序并不相同，往往与理论上这些金属的凝结序列不一致。
阿伦德陨星里的陨石球粒和 内含物是由球粒陨石基质结合到一起的，这是一种细粒混合物，主要是硅酸盐矿物，也包含铁颗粒和硫化亚铁。人们一度认为这些基质颗粒可能只含有星云尘埃，也 就是形成陨石球粒和内含物的物质。不过对球粒陨石基质的详细研究表明多数基质的确是由星云的凝结和熔融形成的，但是在这些经过凝结和熔融的物质中还混有小 部分残留的星际尘埃。
所有这些各种各样的组分被凝聚到一起形成了球粒陨石，就像与太阳具有很多相似化学组分的阿伦德陨星。为了比较陨星和太 阳的组分，我们需要比较元素的比率，而不是简单的比较原子的丰度。毕竟，太阳含有的任何一种元素的原子数都要比一块陨星样品含有的多，但是两者间的铁和硅 之比可能是具有可比性的。结果我们发现它们在组成上具有惊人的相似性。主要的差别是相比太阳，阿伦德陨星失去了大部分的挥发性元素，例如氢、碳、氧、氮以 及惰性气体。这些元素即使是在很低的气温下也倾向于形成气体。我们或许会认为球粒陨石是“蒸馏后的太阳”的样本，有点像太阳除去了气体后的沉淀物。由于太 阳系的质量几乎都集中于太阳，这种相似的化学组成意味着除了大部分的挥发性元素外，球粒陨石具有正常的太阳系组成，它们是真正星云物质的团块，很可能与形 成行星的物质具有相似的组成。
