TOEFL Reading: ETS-TOEFL阅读机经 - U35INEIW4X53Y197L$

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 presence of only very small invertebrates on a reef is an indication of widespread predation. B. Most reefs are structured in a way which allows small invertebrates to remain hidden or camouflaged. C. Almost all small invertebrates are hidden or camouflaged, indicating the extent and importance of predation to reef structure. D. Almost all of the small invertebrates on reefs are difficult to find because they are so highly camouflaged.