扫描二维码，直接登录
题库 / Prep2012-CR-73
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 been unusually 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.
听了Ron大神的解说，仔细想想就一个很简单的原理：每年的增量*年数=最后的总增量
所以年数=总增量/年增量，已知最后的总增量相同，要保证年数正确，就要使年增量相同，也就是年增量每年都一样，也就是A。
E即使盐被一些生物消耗，但只要保证年增量一样，最后的年数也是一样的。
听了Ron大神的解说，仔细想想就一个很简单的原理：每年的增量*年数=最后的总增量
所以年数=总增量/年增量，已知最后的总增量相同，要保证年数正确，就要使年增量相同，也就是年增量每年都一样，也就是A。
E即使盐被一些生物消耗，但只要保证年增量一样，最后的年数也是一样的。
听了Ron大神的解说，仔细想想就一个很简单的原理：每年的增量*年数=最后的总增量
所以年数=总增量/年增量，已知最后的总增量相同，要保证年数正确，就要使年增量相同，也就是年增量每年都一样，也就是A。
E即使盐被一些生物消耗，但只要保证年增量一样，最后的年数也是一样的。
听了Ron大神的解说，仔细想想就一个很简单的原理：每年的增量*年数=最后的总增量
所以年数=总增量/年增量，已知最后的总增量相同，要保证年数正确，就要使年增量相同，也就是年增量每年都一样，也就是A。
E即使盐被一些生物消耗，但只要保证年增量一样，最后的年数也是一样的。
The quantities of dissolved salts deposited by rivers in the Earth's oceans have not been unusually large 说明是一个稳定的状态
B的错误在于 只提到river，明显的与题意不符，river是一直减少的趋势，如果是river和ocean应该就OK吧
E-即使有生物活动消耗盐也没关系，只要这几百年river载着均速的稳定数量的盐到海里
A-说river里溶解的盐的量在几百年都不是很多，正确
其实E和C的道理是一样的，如果E对的话，那么C也有道理，但最终还是A最有道理