单选题
The Greatest Mystery Of Whales
The whale is a warm-blooded, air-breathing animal, giving birth to its young alive, sucking them—and, like all mammals, originated on land. There are many front flippers (鳍状肢), used for steering and stability, are traces of feet,
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of this. Its immense strength is
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into the great body of the big whales, and in fact most of a whale"s body is one gigantic muscle. The blue whale"s pulling strength has been estimated
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400 horsepower. One specimen was reported to have towed (拖) a whaling vessel for seven hours at the
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of eight knot (节).
An angry whale will
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. A famous example of this was the fate of Whaler Essex,
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was sunk off the coast of South America early in the last century. More recently, steel ships have
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their plates buckled (使弯曲) in the same way. Sperm whales (抹香鲸) were known to seize the old-time whaleboats in their jaws and crush them.
The greatest
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of whales is their diving ability. The sperm whale dives to the bottom for his
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food, the octopus (章鱼). In that search he is known to go as far down as 3,200 feet, where the
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is 1,400 pounds, to a square inch. Doing so he will
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underwater long as one hour. Two special skills are involved in this storing up enough
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(all whales are air-breathed) and tolerating the great change in pressure. Just how he does it scientists have not
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. It is believed that some of the oxygen is stored in a special
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of blood vessels, rather than just held in the lungs. And it is believed that a special kind of oil in his head is some sort of compensating mechanism that
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adjusts the internal pressure of his body. But since you can"t bring a live whale into the laboratory for study, no one knows just how these things work.