Scientists have long sought the reasons for the relatively young age of

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问题       Scientists have long sought the reasons for the relatively young age of the
   majority of Martian meteorites discovered on Earth in comparison with the age
   of Mars, an enigma exacerbated by the fact that the Martian rocks were ejected
   by only six or seven separate impact events. Previous tests had predicted that
(5) driving meteorites to Earth would require a collision with an asteroid immense
   enough to make a crater 12-kilometers across, but because such huge impacts
   are extremely infrequent, it was unlikely that enough of them could have
   occurred to explain our planet’s Martian meteorite collection.
      Now astronomer James Head’s higher-resolution models demonstrate that
(10)  collisions making craters only three kilometers across can jettison 10 million
   fragments, each about 10 centimeters across,  into space,  a distribution
   sufficient to cause some of them to be found on Earth. Sections of the planet
   covered by debris (thus likely to be made up of older terrain) would require
   larger and hence rarer impacts, and thus meteorites which reach Earth are
(15)  predictably biased toward younger ages.

选项 A、presenting an argument to support a particular hypothesis
B、suggesting an answer to a theoretical question
C、questioning the assumptions of a research project
D、criticizing experimental results
E、explaining the origin of certain scientific data

答案 B

解析

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