TOEFL Reading: ETS-TOEFL阅读机经 - 71039BE333R47H67L$

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. Zooplankton move up into surface waters at night to feed on phytoplankton, and down into deep, dark waters in daytime to avoid detection by predatory fish. B. Zooplankton migrate vertically on a daily basis in order to feed on phytoplankton, following them up into surface waters by day and down into dark, deeper waters at night. C. Unlike zooplankton, which migrate between surface waters and deeper waters, predatory fish must rely on the daytime light of surface waters to detect prey. D. Zooplankton are so tiny that they can only be detected by predatory fish in the light conditions of surface water, where they feed on phytoplankton.