请教大全-3-14，没人问过

Of the countries that were the world’s twenty largest exporters in 1953, four had the same share of total world exports in 1984 as in 1953. These countries can therefore serve as models for those countries that wish to keep their share of the global export trade stable over the years.

Which of the following, if true, casts the most serious doubt on the suitability of those four countries as models in the sense described?

(A) Many countries wish to increase their share of world export trade, not just keep it stable.

(B) Many countries are less concerned with exports alone than with he balance between exports and imports.

(C) With respect to the mix of products each exports, the four countries are very different from each other.

(D) Of the four countries, two had a much larger, and two had a much smaller, share of total world exports in 1970 than in 1984.

(E) The exports of the four countries range from 15 percent to 75 percent of the total national output.

请问为什么选D呀？？？

条件是：4个国家的总份额保持不变。结论是：4个国家可以作为稳定份额的例子＝4个国家份额分别都很稳定。要使条件和结论保持一致，搭桥：4个国家的总份额不变是因为分别的份额都没有变。

削弱就是断桥，D说两个国家份额加大两个国家份额减小（总份额仍然保持不变），打破了分别不变的桥，削弱。

携隐JJ，我好好看了一下题目和选项，发现原来是因为我没注意到时间的变化，题目中说的是1984和1953，而D选项说的是1970和1983，时间不一样，这是接这道题的关键

而JJ你说的总和分别，我觉得题目里并没有这个意思，JJ，你对这道题的理解我觉得有偏差啊

四国从1953---1984是没变,但1953--1970变化了啊.说明他们的稳定不是持久的,不确切的说,四国1984和1953出口一样只是巧合