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  3. Hydrothermal vents along the mid-ocean ridges host ephemeral ecosystems of diverse fauna, including several crustacean spe

Hydrothermal vents along the mid-ocean ridges host ephemeral ecosystems of diverse fauna, including several crustacean spe

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问题             Hydrothermal vents along the mid-ocean ridges host ephemeral ecosystems
      of diverse fauna, including several crustacean species, some of which undergo
      development as larvae up to 1,000 meters above and 100 kilometers away from
Line   the vents. For example, vent crab Bythograea thermydron (at stage of
(5)    larvae) possess image-forming compound eyes with a visual pigment sensitive to
      the blue light of upper oceanic waters. As these larvae metamorphose into
      adulthood and begin to descend to and settle at the vents, they lose their image-
      forming optics and develop high-sensitivity naked-retina eyes. With maturation,
      the spectral absorbance of the visual pigment in these eyes also shifts towards
(10)   longer wavelengths and this progressive visual metamorphosis trades imaging
      for increased sensitivity, and changes spectral sensitivity to the dim, longer
      wavelengths of light existing at the bottom of the ocean. As hydrothermal vents
      produce light, vision may supplement thermal and chemical senses to orient
      post-larval settlement at vent sites.
According to the passage, the optics of the vent crab Bythograea thermydron (line 4) serve all of the following purposes over the course of its life-cycle EXCEPT
选项 A、They assist in the orientation process by helping the crab navigate toward post-larval settlements.
B、They assist the crabs visually by permitting imaging in the light-saturated upper oceanic depths.
C、They help the crabs navigate by providing thermal and chemical senses to the adult crab near post-larval settlements.
D、They increase the crabs’ flexibility by allowing the crab to adapt to two different environments with different lighting conditions.
E、They permit the crabs to achieve increased sensitivity to the location of underwater thermal vents.
答案C
解析
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