理工类A级：完形填空Earths Inner Core
Scientists have long struggled to understand what lies at the planets center， Direct observation of its center is impossible，so researchers must_____(51)to other evidence.
In 1889，a German scientist detected a severe earthquake in Japan.Geophysicists concluded that shock waves_____(52)jolts(晃动)from one side of Earth through the center to the other side.Then in 1936，Danish geophysicist Inge Lehmann studied the waves______(53) to determine that within Earths core of molten(熔化了的)iron lies a solid inner core-but_____ (54)that core was made of eluded(难倒)her.Other geophysicists quickly determined that Lehmanns inner core was composed mostly_____(55)iron. Since then， Lehmanns discovery has_____(56)conventional Earth science.
But now scientists are challenging traditional theory with new and radical _____(57) For example，Earths center could actually contain an"inner core within the inner core，claim Ishii and colleague Adam Dziewonski.
Analyzing hundreds of thousands of earthquake wave _____(58)，they maintain that the inner core has at its heart a tiny， even more solid sphere(球体) . This spheremay be the oldest fossil____(59)from the formation of Earth，"says Dziewonski.
Dziewonski and Ishii speculate that shortly_____(60) Earth formed around 4.8billion years ago，a giant asteroid(小行星)smashed into the young planet and nearly melted it. But Earths center didnt quite melt;it______(61)mass as the planet cooled. The core within a core may be the kernel(核心)that endured."Its presence could change our basic ideas about the_____ (62)of the planet，"Dziewonski says idea is tame(温和的)compared to the_____(63)theories of independent geophysicist J.Marvin Herndon.Earths inner core is made not of iron，he claims but a_____(64)of nickel and silicon Hemdon has a truly revolutionary notion：Within the nickel silicide(硅化物)inner core is also an"inner"inner core-an 8 km-wide ball of the element uranium.Uranium is radioactive.Hemdon thinks the uranium releases heat energy as its atoms_____(65)fission-split and crash into another in a chain reaction. In other words，we may live on top of a gigantic， "natural"nuclear power plant.
51 A try B leave C turn D point
52 A create B receive C feel D overcome
53 A work B solution C job D patterns
54 A whether B what C why D how
55 A from B within C of D to
56 A followed B dominated C restored D opposed
57 A ideas B demands C phenomena D movements
58 A things B acts C methods D records
59 A taken B benefited C left D kept
60 A after B before C since D when
61 A expanded B modified C gained D melted
62 A size B origin C structure D shape
63 A radical B traditional C classical D conventional
64 A system B copy C model D compound
65 A charge B last C experience D show
答案：
51 C turn to other evidence：寻求其他证据。Tum to属固定搭配。
52 A create jolts：造成震动。其他几个选项意思不符。
53 D wayespatterns：波浪的形状。科学家通过研究震波的形状了解地球的情况。
54 B 此处的意思是地心是由什么构成的难倒了她。这里应使用what构成名词性从旬，作主语。
55 C compose of：由……组成。固定短语。
56 B dominate：占统治地位，支配。Lehamann的发现在传统地球科学领域占统治地位。
57 A 此处的意思是：现在的科学家正用新的、激进的观点挑战传统的理论。本题只有填ideas才符合本句的意思。
58 D 此处填records，本句的意思是：通过分析数十万次地震波的记录，他们认为……。其他几个选项与句意不符。
59 C left：留下来的。此处的意思是：这一球体可能是地球形成时留下来的最古老的化石。
60 A 依据上下文，应用afte~句子意思才讲得通。
61 C gain：获取。gained mass as the planet cooled：在星球(这里指地球)变冷的过程中，它逐渐获得了质量。
62 B 本文主要谈地球起源问题，故此处应填ongm.
63 A 本句前面出现的一个词是"tame"，与之对应，应该是"radical".
64 D nickel和silicon的混合物，compound：混合物。
65 C fission-split：裂变。经历裂变，用动词experience.