The Greatest Mysteryof Wha1eg

The whale is a warm一blooded,air-breathing animal,givingbirth to its young alive,sucking them一and,

like allmammals,originated on land. There are many__________(51)of this. Its frontflippers (鳍状肢）,

used for steeringand stability,are traces of feet.

Immense strengthis________(52)into the great body of the big whales,and in fact most of a

whale',body is onegigantic muscle.The blue whale'S pulling strength has beenestimated________.(53)

400 horsepower. Onespecimen was reported to have towed（拖）。whaling vessel for seven hours at the

_______(54)of eightknot（节）.

An angry whalewill________(55).A famous example of this was the fate of Whaler Essex,

________(56)was sunkoff the coast of South America early in thelast century.More recently,steel ships

have_(57)their platesbuckled（使弯曲）in the sameway. Sperm whales（抹香鲸）were known

to seize theold-time whaleboats in their jaws and crush them.

Thegreatest________(58)of whales is their diving ability.The sperm whale dives tothe bottom for

his________(59)food,theoctopus（章鱼）,In that searchhe is known to go as far down as 3 , 200 feet,

wherethe________(60)is 1,400 pounds,to a square inch.Doing so hewill________(61)underwa-

ter as long as onehour. Two special skills are involved in this storing up enough________(62)(all

whales areair-breathed)and tolerating the great change in pressure.Just how he does itscientists have not

_________(63).It isbelieved that some of the oxygen is stored in a special________(64)of blood

vessels,rather thanjust held in the lungs.And it is believed that a special kind of oil in hishead is some sort

of a compensatingmechanism that_________(65)adjusts the internal pressure of his body.But sinceyou

can't bring a livewhale into the laboratory for study,no one knows just how these things work._________(51)

A.aspects

B. signs

C. ways

D. reasons