Passage IV Column 2 heading

31. One of the main ideas established by the passage is that:

  • A. researchers have nearly exhausted their resources
    after spending decades investigating the Sargasso Sea.

  • B. significant gaps still remain in researchers’ understanding
    of the life cycle of eels.

  • C. eels live their entire lives in the Sargasso Sea, but
    no one has ever seen them there.

  • D. female eels turn into silver eels toward the end of
    their lives.