Whales originated in the freshwater lakes and rivers of ancient Asia about sixty million years ago.Not until about ten million years later did species of whales develop specialized kidneys enabling them to drink salt water.Although fossil evidence shows that some early whale species that lacked such kidneys sometimes swam in the Earth’s saltwater oceans, these species must have had to return frequently to freshwater rivers to drink.
Which of the following is most strongly supported by the information given?
A.Fossils of whale species dating from between sixty million and fifty million years ago will not be found on continents that were at the time separated from ancient Asia by wide expanses of ocean.
B.Among whale fossils that date from later than about fifty million years ago, none are fossils of whale species that drank only fresh water.
C.Fossils of whale species that drank fresh water will not be found in close proximity to fossils of whale species that drank salt water.
D.The earliest whales that drank salt water differed from fresh-water-drinking whales only in their possession of specialized kidneys.
E.Between sixty million and fifty million years ago, the freshwater lakes and rivers in which whales originated were gradually invaded by salt water.
E为什么错，谢谢，因为我觉得金鱼到盐水了再回去淡水会使淡水盐分增加。。。。 请朋友门解释下。。 作者: rudder26 时间: 2010-7-12 19:30
顶啊 啊 啊啊作者: samwzhang 时间: 2010-7-12 22:02
Evidence 1: Whales originated in the freshwater lakes and rivers of ancient Asia about sixty million years ago;
Evidence 2: Not until about ten million years later did species of whales develop specialized kidneys enabling them to drink salt water
Evidence 3: fossil evidence shows that some early whale species that lacked such kidneys sometimes swam in the Earth’s saltwater oceans
Conclusion: these species must have had to return frequently to freshwater rivers to drink
Option E does not establish a link between the conclusion and any of the evidence. Even if the freshwater lakes and rivers were invaded by salt water, the early wales do not nessisarily have to return to freshwater to drink. It would be possible that the early wales were able to adapt to salt water sooner, therefore eliminating the need to rely on freshwater drinking, and consequently counter the conclusion.
Option A clearly establishes links between conclusion and evidence 1, 2 and 3. Because wales originated in freshwater lakes in Asia, and because they wouldn't be able to drink saltwater until 10 million years later, they would not be able to make long distance journies arcross oceans, despite of their abilities to remain in saltwater for a relatively short period of time. Option A supports these points logically.作者: rudder26 时间: 2010-7-12 22:07
THX a lot:0