[請益] TPO 15

[poutery (poutery)]

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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◆ From: 114.26.23.106
推 Ace8633:這段在澄清對於"RECUR PERIODICALLY"的理由假設
推 momo4th:have recurred periodically