TOEFL Reading: ETS-TOEFL阅读机经 - KGV125G1HYFT3ZWRL$

Why does the author conclude in paragraph 8 about the causes of sudden population increases of Acanthaster? A. A sudden population increase in the Acanthaster population could be attributed to natural process as well as human activities. B. There are no elements of truth in the hypothesis proposed to explain sudden population increases of Acanthaster. C. It is possible to offer a single explanation for sudden population increases of Acanthaster. D. Natural processes have been responsible for sudden population increases of Acanthaster in the past while present outbreaks are due to human activities.