标题: GWD9-Q29神马意思?求助各位啦···· [打印本页] 作者: shoufu 时间: 2011-1-30 07:22 标题: GWD9-Q29神马意思?求助各位啦···· The Earth’s rivers constantly carry dissolved salts into its oceans.Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an assumption on which the argument depends?
The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not beenunusually large during the past hundred years.
At any given time, all the Earth’s rivers have about the same salt levels.
There are salts that leach into the Earth’s oceans directly from the ocean floor.
There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans. 作者: Lacus 时间: 2011-1-30 10:12
题目给出的意思是:(当前海水含盐水平-最初的海水含盐水平)/每年输入海水的盐水平=海洋的寿命,且分子 是确定的。要保证最后的结果正确,则必须保证输入盐水平是均匀的。作者: shoufu 时间: 2011-1-31 08:39
万分感谢,晓了,呵呵作者: Siegfred 时间: 2011-11-24 12:56
原来如此啊, mark下