3 Select the correct answer.
How does the author's use of the word "tusk" inform the reader?
OA It demonstrates that large marine mammals prefer to gather in coastal areas.
OB. It serves to emphasize the fact that wild creatures tend to thrive in their natural habitat.
OC it invites comparisons to more familiar animals with a similar feature, such as elephants.
OD. It suggests an aggressive and relentless nature, such as sharks and orca possess.
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excerpt adapted from The Unicorn of the Sea
by the National Oceanic and Atmospheric Administration
The narwhal is a toothed whale, but it is different from all other toothed whales in that it
has no teeth in its mouth. Instead, male narwhals have a single, long, straight tooth (or tusk)
that protrudes two to three meters out of the upper left jaw. Females almost never have a
tusk. The tooth grows in a counterclockwise spiral
It is this tusk for which narwhals are best known. There are many legends about the tusk
of the narwhal. It is essentially the origin of the myth of the unicom-European whalers that
were in the Arctic would catch narwhals and bring tusks back to Europe with great stories
about what kind of animals the tusks were attached to. But in terms of the biology of the
animal the tusk is actually used for social structure to establish hierarchies of dominance
for the males within narwhal pods. Narwhals have a black-and-white mottled skin pattern
and are white underneath. The scientific name for these whales. Monodon monoceros.
means "one tooth, one horn"
Not very much is known about narwhals, largely because they are difficult to study. They
live in remote places, far from civilization, in a habitat that is dark for one half the year.
covered in ice for the other half of the year, and not easy to access
We do know that narwhals have adapted to be one of the deepest diving marine
mammals capable of diving to depths of more than 1.800 meters and able to spend a large
amount of their time below 800 meters. Not many animals can sustain such intense
pressures below the surface of the water and stay under the water for so long
The primary prey of narwhals include Greenland halibut polar and Arctic cod, shrimp, and
squid. They change their diets seasonally, feeding intensely in the winter and eating little
during the ice free summer season. This feeding pattern is the opposite of other subarctic
whale species, who tend to migrate south in the winter and feed in the summer. Scientists
believe the narwhal's intense winter feeding period may be an adaptation to relatively low
productivity in the high Arctic summering areas or perhaps a behavioral trait to avoid
competition with lower-latitude whales feeding in summer.