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 (51) of this. Its front flippers (鳍状肢), used for steering and stability, are traces of feet.
Immense strength is (52) 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 (53) 400 horsepower. One specimen was reported to have towed (拖) a whaling vessel for seven hours at the (54) of eight knots (节).

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