共用题干
The Greatest Mystery of Wha1eg
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',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）。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 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)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 not
_________(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