题型分类：文章总结题

题干分析：选择概括性的正确选项。

选项分析：

A 选项是综合了第二段和第三段的重要信息，为两段的概括性总结。Rhipidistian crossopterygian had features such as primitive lungs and thick fins that could have helped it survive dry periods 对应第二段的第四、五、六句 If there were periods of drought, any adaptations allowing the fish to survive the dry conditions would have been advantageous... It is known that they had lungs as well as gills for breathing。和第三段的前三句 A second adaptation of these fish was in the structure of the lobe fins. The fins were thick, fleshy, and quite sturdy, with a median axis of bone down the center... perhaps good enough to allow a fish to flop its way from one pool of water that was almost dry to an adjacent pond that had enough water and oxygen for survival。

D 选项对应第四段的重要信息。A drier climate 对应第四段的第二句 Changes in climate... if freshwater areas became progressively more restricted，new sources of food 对应第四段的第三句 Another impetus may have been new sources of food 第四段后面就是对此展开的具体例子说明。

F 选项对应第五段的重要信息。Early tetrapods remained closely connected to water 对应第五段的第二句 ... they were still quite tied to water，but several of their body structures were adapted for life on land 对应第五段的最后一句 The principal changes for the earliest tetrapods were in the skeletal system—changes in the bones of the fins, the vertebral column, pelvic girdle, and pectoral girdle。

B 选项中使用 preferred 这个词在文中没有表达过与此相关的意思。无中生有。

C 选项说到鳍的骨骼数量增加，提升了游泳和陆上移动能力，而文中最后一句 The principal changes for the earliest tetrapods were in the skeletal system—changes in the bones of the fins, the vertebral column, pelvic girdle, and pectoral girdle 并没有说骨骼数量的增加。无中生有。

E 选项说在四足动物出现肺不久，植物和其他动物在陆地上发展起来。而原文中 developed lungs 的内容出现在第二段，用来说明鱼进化的一个适应性改变。plants and other animals began to flourish on land 出现在第四段，用来说明鱼进化成陆生生物的原因。两者之间在文中并无关联，也不存在先后顺序。