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  3. All whales fall into two groups, those with teeth and those without. Both beluga and dolphin belong to the suborder of toothed w

All whales fall into two groups, those with teeth and those without. Both beluga and dolphin belong to the suborder of toothed w

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问题     All whales fall into two groups, those with teeth and those without. Both beluga and dolphin belong to the suborder of toothed whales known as Odontoceti, along with porpoises, narwhals, pilot whales, killer whales and the largest toothed creature in the world, the sperm whale. Size differences among the Odontoceti are remarkable. A common porpoise will run only 4 or 5 feet in length and 300 pounds in weight; a sperm whale may be 10 times as long and 300 times as heavy. The beluga falls in between, weighing up to 2,000 pounds. And it does chirp. In fact, it makes a great variety of squeaking, whistling, and clicking sounds, which have earned it the name of sea canary.
    The toothless, or baleen, whales belong to the suborder of Mysticeti. This is a group of generally large whales, formerly abundant in all the oceans of the world. Though reduced by hunting, most species are still found along the coasts of the United Stated and Canada. All but two of the Mysticeti reach 40 feet or more at maturity, with the blue whale running up to 100 feet and tipping the scales at up to 130 tons. This whale is by far the largest creature that has ever lived on earth, 4 times the weight of the largest dinosaur, 30 times that of an elephant.
Which of the following is mentioned by the author as a reason why the baleen whale population has been reduced?
选项 A、Increased pollution of the seas.
B、Hunting.
C、Insufficient supply of food.
D、Disease.
答案B
解析 文章第二段中“Though reduced by hunting…”一句告诉我们此种鲸变少的原因在于捕杀，因此选B。
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