Re: [請益] TPO 15
看板TOEFL_iBT (TOEFL_iBT托福)作者Merica (美加文教)時間15年前 (2011/03/15 10:44)推噓0(0推 0噓 0→)留言0則, 0人參與討論串2/2 (看更多)
因為第二、三行都有提到episodes have recurred periodically, approximately every
26 million years since the mid-Cretaceous period.
(以上內容由美加 林子育老師提供)
※ 引述《poutery (poutery)》之銘言：
: American paleontologists David Raup and John Sepkoski, who have studied
: extinction rates in a number of fossil groups, suggest that episodes of
: increased extinction have recurred periodically, approximately every 26
: million years since the mid-Cretaceous period.The late Cretaceous
: extinction of the dinosaurs and ammonoids was just one of the more drastic
: in a whole series of such recurrent extinction episodes. The possibility
: that mass extinctions may recur periodically has given rise to such
: hypotheses as that of a companion star with a long-period orbit deflecting
: other bodies from their normal orbits, making some of them fall to Earth as
: meteors and causing widespread devastation upon impact.
: According to paragraph 4, what aspect of extinction episodes does the companion
: -star hypothesis supposedly clarify?
: ○Their location
: ○Their frequency
: ○Their duration
: ○Their severity
: 答案是B
: 我覺得答案在最後一句,可是又看不出來為什麼..
: 麻煩高手們看一下 謝謝
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