TOEFL Reading: ETS-TOEFL阅读机经 - E899V3HVZT16WFT5L$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. The fern spike is the term given to this sudden increase in the abundance of fern spores blown into the oceans around the world. B. The sudden increase in fern spores occurred in exactly the same parts of the world where the plankton was disappearing. C. Fern spores have even been found in some marine deposits from exactly the same layer as that showing the disappearance of the plankton. D. Most marine deposits from around the world contain either plankton or a lot of fern spores but not both together in the same layer.