[不定项选择题]共用题干 The Greatest Mystery of Whales

The whale is a warm一blooded,air-breathing animal,giving birth to its young alive,sucking them一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 Essex,
________________(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 foi
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)underwa-
ter as long as one hour. Two special skills are involved in this storing up enough________________(62)(all
whales are air-breathed)and tolerating the great change in pressure.Just how he does it scientists have nol
_______________ (63).It is believed that some of the oxygen is stored in a special________________(64)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 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. _________(54)
A.number
B.degree
C.distance
D.rate