The whale is a mammal-warm-blooded, air-breathing, giving birth to its young alive. sucking them-and, like all mammals, originated on land. There are many signs of this. Its front flippers (鳍足), used for steering and stability, are traces of feet. Immense strength is built 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 at 400 horsepower. One specimen was reported to have towed (牵引) a whaling vessel for seven hours at the rate of eight knots. An enraged whale will attack a ship. A famous example of this was the fate of whaler Essex, which was sunk off the coast South America early in the last century. More recently, steel ships have had their plates buckled in the same way. Sperm whales were known to seize the old-time whaleboats in their jaws and crush them. The greatest mystery of whales is their diving ability. The sperm whale can dive on the bottom for his favorite food, the octopus. In that search he is known to go as far down as 3,200 feet, where the pressure is 1,400 pounds, to the square inch. Doing so he will remain submerged as long as one hour. Two feats(壮举) are involved in this: storing up enough oxygen (all whales are air-breathed) and withstanding the great change in pressure. Just how he does it scientists have not determined. It is believed that some of the oxygen is stored in a special system 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 compensating mechanism that automatically 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.
单选题
Which of the following is a sign of the fact that the whale originated from the land?
单选题
The blue whale's pulling strength can be as great as
【正确答案】
A
【答案解析】根据题干定位到第二段第二句：The blue whale's pulling strength has been estimated at 400 horsepower(蓝鲸的拖力据估计可以达到400码力)，很显然正确答案为A。其他三个数字也在文中出现，但B和C分别说的是鲸的潜水深度和能承受的压力，而D选项是第二段中的数字，说一种鲸曾经拖着捕鲸船以八节(节：海上航行时速单位)的时速拖行了七个小时，因此也被排除在外。
单选题
Fate of whaler Essex is an example of
【正确答案】
A
【答案解析】根据题干定位到第三段的前两句：An enraged whale will attack a ship. A famous example of this was the fate of whaler Essex, which was sunk off the coast South America early in the last century(被激怒的鲸会攻击船只，一个著名的例子就是捕鲸船Essex的命运，他在上个地纪沉没在南美洲的海岸)，很显然本题的正确答案为A。
单选题
What is important for whale's great diving ability?
【正确答案】
B
【答案解析】根据题干定位到最后一段第五句：Two feat are involved in this: storing up enough oxygen... and withstanding the great change in pressure(在这里涉及了两种重要行为：储存足够的氧气和承受巨人的压力变化)，A选项的前半部分没有问题，但是后面部分in their lungs与文章后面的文字不符：科学家还不知道鲸是如何做到上面两点的，科学家们认为氧气是储存在特殊的血管系统当中，而不是肺部，由此我们排除了A。B选项与句中的叙述完全一致，因此为正确答案。其他两点都是鲸的特点，但不是他具有神奇的潜水能力的原因，故排除。
单选题
What is the reason that scientists cannot yet explain the great diving ability of the whales?
【正确答案】
C
【答案解析】根据题干定位到最后一段的结尾处：But since you can't bring a live whale into the laboratory for study, no one knows just how these things work(既然无法将一头鲸活着弄进实验室来研究，没人能够解释这些——体内特殊的血管网络和头部特殊的油脂——到底是如何工作的)。显然本题的正确答案为C。