Html Bootstrap 3.4使用图像时的网格布局问题

我遵循一个引导教程制作一个简单的照片库。使用网格系统对我来说完全有意义，但当我遵循教程时，我会得到不同的结果。3x3网格中应该有9个图像，但由于某种原因，某些图像被“推/拉”出了位置。谢谢你的帮助

代码：

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最可能的原因是您忘记在代码中添加到引导CDN的链接

审判

最可能的原因是您忘记在代码中添加到引导CDN的链接

审判

<div class="container"> 
    <div class="row">   
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596877098462-fd1cfc6482c4?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1587712606457-20d42e24300e?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596716999716-544f09b06743?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>        
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596716999716-544f09b06743?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>        
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596716999716-544f09b06743?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>        
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596716999716-544f09b06743?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596716999716-544f09b06743?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>        
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596716999716-544f09b06743?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>        
            <div class="col-lg-4 "> <img class="img-thumbnail" src="https://images.unsplash.com/photo-1596716999716-544f09b06743?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=500&q=60" alt=""></div>
    </div>

</div>