题目解析：
【题目翻译】根据第3段，泥盆纪扇鳍鱼的鳍的结构可能允许这些鱼
A：减少生存所需的氧气量
B：骨骼粗壮。
C：在水中更有效地移动
D：在大部分干燥的地方短距离移动。
【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。
【关键词定位】：根据关键词“he structure of the fins”,定位到Passage 3 第2、3句，原句为“The fins were thick, fleshy, and quite sturdy, with a median axis of bone down the center. They could have been used as feeble locomotor devices on land, 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. ”，意思是“鱼鳍很厚，肉质，非常结实，中轴骨位于中央。它们可能被用作陆地上微弱的运动装置，也许足够好让鱼从一个几乎干燥的水池中扑通扑通地游到附近一个有足够的水和氧气生存的水池中。”。
【逻辑分析】：结合题目问法和出题句，进行逻辑分析。
【选项分析】
A：文章中：使它可以去到有足够氧气的地方。而不是减少氧气量。故选项错误。
B：没有提到骨骼粗壮。故选项错误。
C：文章中：“扑通扑通地移动”说明移动并不是很有有效。故选项错误。
D：符合文意，正确。
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. They could have been used as feeble locomotor devices on land, 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. These fins eventually changed into short, stubby legs. The bones of the fins of a Devonian rhipidistian exactly match in number and position the limb bones of the earliest known tetrapods, the amphibians. It should be emphasized that the evolution of lungs and limbs was in no sense an anticipation of future life on land. These adaptations developed because they helped fish to survive in their existing aquatic environment.
