共用题干 The Greatest Mystery of WhalesThe whale is a warm-blooded,air-breathing animal,giving birth to its young alive,ing 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 knot(节).An angry whale will______(55).A famous example of this was the fate of Whaler Es, ______(56)was sunk off the coast of South America early in the last century.More recently,steel ships have______( 57 ) 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______(58)of whales is their diving ability.The sperm whale dives to the bottom for his______( 59 ) food , the octopus(章鱼).In that search he is known to go as far down as 3 , 200 feet, where the______(60)is 1,400 pounds to a square inch.Doing so he will______(61) underwater as long as one hour.Two special skills are involved in this storing up enough______(62) (all whales are air-breathed)and tolerating thern great change in pressure.Just how he does it scientists have not______(63).It is believed that some of the oxygen is stored in a special ______()of blood vessels,rather than just held in the lungs.And it is believed that a special kind of oi1 in his head is some sort of a compensating mechanism that______(65)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. 51._________