GRE Reading Comprehension

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Source: NO9

Zooplankton, tiny animals adapted to an existence in the ocean, have evolved clever mechanisms for obtaining their food, miniscule phytoplankton (plant plankton). A very specialized feeding adaptation in zooplankton is that of the tadpolelike appendicularian who lives in a walnut-sized (or smaller) balloon of mucus equipped with filters that capture and concentrate phytoplankton. The balloon, a transparent structure that varies in design according to the 　　type of appendicularian inhabiting it, also protects the animal and helps to keep it afloat. Water containing phytoplankton is pumped by the appendicularian's muscular tail into the balloon's incurrent filters, passes through the feeding filter where the appendicularian sucks the food into its mouth, and then goes through an exit passage. Found in all the oceans of the world, including the Arctic Ocean, appendicularians tend to remain near the water's surface where the density of phytoplankton is greatest.

Question List: 1 2 3 4

The passage suggests that appendicularians tend to remain in surface waters because they

  • A prefer the warmer water near the surface
  • B are unable to secrete mucus at the lower levels of the ocean
  • C use the contrast of light and shadow at the surface to hide from predators
  • D live in balloons that cannot withstand the water pressure deeper in the ocean
  • E eat food that grows more profusely near the surface

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