为什么有些鱼类可以既有鳃又有肺，而海洋中的哺乳动物却进化不出来呢? (opens in new tab)

<div class="main-wrap content-wrap"> <div class="headline"> <div class="img-place-holder"></div> </div> <div class="content-inner"> <div class="question"> <h2 class="question-title"></h2> <div class="answer"> <div class="meta"> <img class="avatar" src=" referrerpolicy="no-referrer"> <span class="author">祥昊，</span><span class="bio">哎，本来我是来看段子的，现在好了，段子看我。</span> <a href=" class="originUrl" hidden="">查看知乎原文</a> </div> <div class="content"> <p>这个问题曾经有个鲸鱼问过我，</p> <p>它说它厌倦了每天半夜起夜喘气的日子，想...