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标题: [求助]急，GWD27-22 [打印本页]

作者: happypoor88 时间: 2007-8-9 19:37
标题: [求助]急，GWD27-22

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?

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.
Among whale fossils that date from later than about fifty million years ago, none are fossils of whale species that drank only fresh water.
Fossils of whale species that drank fresh water will not be found in close proximity to fossils of whale species that drank salt water.
The earliest whales that drank salt water differed from fresh-water-drinking whales only in their possession of specialized kidneys.
Between sixty million and fifty million years ago, the freshwater lakes and rivers in which whales originated were gradually invaded by salt water

为什么选A呢？哪位牛人能帮忙解答一下。

作者: elithian 时间: 2007-8-9 19:44

A.因为以前的鲸鱼是喝淡水的，所以不能游泳过太平洋啊！

作者: moonwest 时间: 2009-3-29 01:11

these species must have had to return frequently to freshwater rivers to drink

必须得经常游回去

所以A就不可能一下子游那么远

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