TOEFL Reading: ETS-TOEFL阅读机经 - 50PIES93YXR823QVL$

What is the main purpose of paragraph 4 in the passage? A. To give the details of an adaptation mentioned in paragraph 3 B. To describe an adaptation different from the one explained in paragraph 3 C. To introduce an adaptation that is described in detail in paragraph 5 D. To discuss an adaptation that is set as successful as the one mentioned before.