为什么bootstrap carousel不符合我的图像尺寸？

Question

这是我的旋转木马的代码，我试图用bootstrap＆amp; HTML

<div id="myCarousel" class="carousel slide" style="width: 400px; margin: 0 auto">
  <div class="carousel-inner">
    <div class="item">
      <img src="download.jpg"
      alt="" width="250" height="250">
      <div class="carousel-caption">
         <h4>First Thumbnail label</h4>

        <p>Cras justo odio, dapibus ac facilisis in, egestas eget quam. Donec id
          elit non mi porta gravida at eget metus. Nullam id dolor id nibh ultricies
          vehicula ut id elit.</p>
      </div>
    </div>
    <div class="item">
      <img src="download3.jpg"
      alt="" width="250" height="250">
      <div class="carousel-caption">
         <h4>Second Thumbnail label</h4>

        <p>Cras justo odio, dapibus ac facilisis in, egestas eget quam. Donec id
          elit non mi porta gravida at eget metus. Nullam id dolor id nibh ultricies
          vehicula ut id elit.</p>
      </div>
    </div>
    <div class="item active">
      <img src="download.jpg"
      alt="" width="250" height="250">
      <div class="carousel-caption">
         <h4>Third Thumbnail label</h4>

        <p>Cras justo odio, dapibus ac facilisis in, egestas eget quam. Donec id
          elit non mi porta gravida at eget metus. Nullam id dolor id nibh ultricies
          vehicula ut id elit.</p>
      </div>
    </div>
  </div> <a class="left carousel-control" href="#myCarousel" data-slide="prev">‹</a>

  <a
  class="right carousel-control" href="#myCarousel" data-slide="next">›</a>
</div>

出于某些原因，旋转木马上的图像会改变尺寸，并且当遇到一个特定图像时，旋转木马的尺寸会缩小？

如何防止这种情况？