共用题干 Earth's Inner CoreScientists have long struggled to unders

共用题干 Earth's Inner CoreScientists have long struggled to understand what lies at the planet's 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 lnge Lehmann studied the waves' __________ (3) to determine that within Earth's core of molten(熔化了的)iron lies a solid inner core一but_________(4) that core was made of eluded(难倒)her. Other geophysicists quickly determined that Lehmann's inner core was composed mostly_________(5) iron.Since then,Lehmann's discovery has _________(6) conventional Earth science.But now scientists are challenging traditional theory with new and radical_________(7).For example,Earth's center could actually contain an"inner core within the inner core."claim lshii 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 Earth's center didn't 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.Dziewonski's idea is tame(温和的)compared to the_________( 13 ) theories ofindependent geophysicist J. Marvin Herndon.Earth's 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一an 8km-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. _________(13)

A.radical

B.traditional

C.classical

D.conventional

正确答案是A