2014年职称英语理工类考试完形填空强化练习(9)

　　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___ （1）___ to other evidence.

　　In 1889, a German scientist detected a severe earthquake in Japan. Geophysicists concluded that shock waves ___（2）___ 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 ___（3）___ to determine that within Earths core of molten （熔化了的） iron lies a solid inner core － but ___（4）___ that core was made of eluded （难倒） her. Other geophysicists quickly determined that Lehmanns inner core was composed mostly ___（5___） iron. Since then, Lehmanns discovery has ___（6）___ conventional Earth science.

　　But now scientists are challenging traditional theory with new and radical ___（7）___. 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 ___（8___）, they maintain that the inner core has at its heart a tiny, even more solid sphere （球体）. This sphere may be the oldest fossil ___（9）___ from the formation of Earth, says Dziewonski.

　　Dziewonski and Ishii speculate that shortly ___（10）___ Earth formed around 4.8 billion years ago, a giant asteroid （小行星） smashed into the young planet and nearly melted it. But Earths center didnt quite melt; it ___（11）___ 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 ___（12）___ of the planet, Dziewonski says.

　　Dziewonskis idea is tame （温和的） compared to the ___（13）___ theories of independent geophysicist J. Marvin Herndon. Earths inner core is made not of iron, he claims, but a___ （14）___ of nickel and silicon. Herndon 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. Herndon thinks the uranium releases heat energy as its atoms ___（15）___ fission-split and crash into one another in a chain reaction. In other words, we may live on top of a gigantic, natural nuclear power plant.

　　1 A try B leave C turn D point

　　2 A create B receive C feel D overcome

　　3 A work B solution C job D patterns

　　4 A whether B what C why D how

　　5 A from B within C of D to

　　6 A followed B dominated C restored D opposed

　　7 A ideas B demands C phenomena D movements

　　8 A things B acts C methods D records

　　9 A taken B benefited C left D kept

　　10 A after B before C since D when

　　11 A expanded B modified C gained D melted

　　12 A size B origin C structure D shape

　　13 A radical B traditional C classical D conventional

　　14 A system B copy C model D compound

　　15 A charge B last C experience D show

　　参考答案:

　　1. C 2. A 3. D 4. B 5. C

　　6. B 7. A 8. D 9. C 10. A

　　11. C 12. B 13. A 14. D 15. C