title: Do I have to use container or container-fluid in grid system?
body: <p>I know the similar questions already exist on Stackoverflow but I think the exact one doesn't exist.</p>
  
  <p>Most people say</p>
  
  <p>"You should place <code>.row</code> in <code>.container</code> and <code>.col</code> should be wrapped by <code>.row</code>".</p>
  
  <p>But I don't perfectly get it.</p>
  
  <p>I am aware of I should wrap <code>.col</code> with <code>.row</code> 
  BUT Do I have to wrap <code>.row</code> with <code>.container</code> or <code>.container-fluid</code>?</p>
  
  <p>Is it mandatory?</p>
  
  <p>I think the code below does work well as grid system.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;html&gt;
  
  &lt;head&gt;
    &lt;link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css"&gt;
    &lt;script src="https://code.jquery.com/jquery-3.4.1.min.js" integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"&gt;&lt;/script&gt;
    &lt;script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"&gt;&lt;/script&gt;
    &lt;script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body&gt;
    &lt;!--
      &lt;div class="container-fluid"&gt;
      --&gt;
    &lt;div class="row"&gt;
      &lt;div class="col-md-6 col-sm-4"&gt;
        A
      &lt;/div&gt;
      &lt;div class="col-md-6 col-sm-4"&gt;
        B
      &lt;/div&gt;
      &lt;div class="col-md-6 col-sm-4"&gt;
        C
      &lt;/div&gt;
      &lt;div class="col-md-6 col-sm-6"&gt;
        D
      &lt;/div&gt;
    &lt;/div&gt;
    &lt;!--
      &lt;/div&gt;
      --&gt;
  &lt;/body&gt;
  
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>