题目内容：
根据材料，回答问题。 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 front flippers(鳍状肢), used for steering and stability, are traces of feet,(51)__________of this. Its Immensestrength is(52)__________ into the great body of the big whales, and in fact most of a whale'sbody 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 sevenhours 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 theBottom for his(59)__________ food, the octopus (章鱼). In that search he is known to go as farDown as 3,200 feet, where the.(60)__________ is 1,400 pounds, to a square inch. Doing so hewill(61)__________ underwater long as one hour. Two special skills are involved in this storing upenough(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 isstored in a special(64)of blood vessels, rather than just held in the lungs. And it isbelieved that a special kind of oil in his head is some sort of compensating mechanism that _(65)__________adjusts the internal pressure of his body. But since you can't bring a live whale intothe laboratory for study, no one knows just how these things work.
请在第__(51)__处填上正确答案。 A．aspects
B．signs
C．ways
D．reasons
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