本题改写简单，答案也较容易做，主要注意 history 的两层意思。

请同学们课下再仔细看一下文章的结构。

    Biologists have long maintained that two groups of pinnipeds, sea lions and walruses, are descended from a terrestrial bearlike animal, whereas the remaining group, seals, shares an ancestor with weasels. But the recent discovery of detailed similarities in the skeletal structure of the flippers in all three groups undermines the attempt to explain away superficial resemblance as due to convergent evolution — the independent development of similarities between unrelated groups in response to similar environmental pressures. Flippers may indeed be a necessary response to aquatic life, turtles, whales, and dugongs also have them. But the common detailed design found among the pinnipeds probably indicates a common ancestor. Moreover, walruses and seals drive themselves through the water with thrusts of their hind flippers, but sea lions use their front flippers. If anatomical similarity in the flippers resulted from similar environmental pressures, as posited by the convergent-evolution theory, one would expect walruses and seals, but not seals and sea lions, to have similar flippers.

注意：1、文章结构。首句：long maintained 为旧观点，取非得新观点。

      2、6行出现 But ，但不是新观点。新观点在19 行。

         请同学们课下思考为什么。

      3、12行 convergent evolution ：趋同进化。看懂其后的英文解释。

         这是作者必定给负评价的理论。

      4、原文末句：If 引导的条件从句。注意：（1）条件句要条件成立，主

         句才有意思；（2）条件句的主句有虚拟语气，是与事实相反的情况。

需要注意的题目：

8.  送分题

9.   long-standing view... pinnipeds

本能反应：长期以来的观点是找旧观点，但没有选项是旧观点——首句的改写。

思路：找过旧观点，但没有选项改写，意味着原文中必然存在一个long-standing 长期以来的作者不喜欢的观点——趋同进化论。只有讲过的才会考。

10.   turtles, whales, dugongs    细节定位题

需要注意的题目：

11.   写作手法题

解题方法：排除法

Exercise Twenty-Seven

    The 1960's witnessed two profound social movements: the civil rights movement and the movement protesting the war in Vietnam . Although they overlapped in time, they were largely distinct. For a brief moment in 1967, however, it appeared that the two movements might unite under the leadership of Martin Luther King, Jr.

    King's role in the antiwar movement appears to require little explanation, since he was the foremost advocate of nonviolence of his time. But King's stance on the Vietnam War cannot be explained in terms of pacifism alone. After all, he was something of a latecomer to the antiwar movement, even though by 1965 he was convinced that the role of the United States in the war was indefensible. Why then the two years that passed before he translated his private misgivings into public dissent? Perhaps he believed that he could not criticize American foreign policy without endangering the support for civil rights that he had won from the federal government.