TOEFL Listening: TPO-TOEFL阅读TPO - 18K0M9L6GNMSF458N$

According to paragraph 4, what did all the ideas about the deep sea discussed in paragraph 3 have in common? A. They were all based on Forbes's observations. B. They all challenged Forbes's theory. C. They all presented the deep sea as lifeless. D. They all underestimated the depth of the sea.