自举轮播项目在幻灯片结束时向下移动

Question

<div id="myCarousel" class="carousel slide" data-ride="carousel">
  <ol class="carousel-indicators">
<li data-target="#myCarousel" data-slide-to="0" class="active"></li>
<li data-target="#myCarousel" data-slide-to="1"></li>
<li data-target="#myCarousel" data-slide-to="2"></li>
  </ol>
  <div class="carousel-inner">
<div class="carousel-item active">
  <img class="d-block w-100" src="img/sl01.png" alt="First slide">
</div>
<div class="carousel-item">
  <img class="d-block w-100" src="img/sl02.png" alt="Second slide">
</div>
<div class="carousel-item">
  <img class="d-block w-100" src="img/sl03.png" alt="Third slide">
</div>
  </div>
  <a class="carousel-control-prev" href="#myCarousel" role="button" data-slide="prev">
<span class="carousel-control-prev-icon" aria-hidden="true"></span>
<span class="sr-only">Previous</span>

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项目在幻灯片结束时向下移动，并在第一个圆圈后继续移动:(（（bootstrap 4