Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, which, causing plant and animal extinctions, marks the end of the geologic era known as the Cretaceous Period.


which, causing plant and animal extinctions, marks

which caused the plant and animal extinctions marking

and causing plant and animal extinctions that mark

an event that caused plant and animal extinctions, and it marks

an event that caused the plant and animal extinctions that mark

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Prep2007E2-SC