没有四肢不仅更适合游泳，也更适合钻洞。 这也引发了关于爬行类动物进化的问题。
Not only is it more efficient to swim without limbs, burrowing without legs is also better, and this raises questions about the twists and turns of reptilian evolution.
夏日在池塘里游泳，四肢击水前进，感觉非常自然。
Swimminging in a summer pond, we notice how natural it is to use all four limbs to travel along.
允许游泳运动员的鳍状肢臂技术集中精力，因为它能有效运作的每一踢，帮助保持发展势头。
Flippers allow the swimmer to concentrate on arm technique because it improves the efficiency of each kick, helping to maintain momentum.
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