title: How to make an if statement to disable select option?
body: <p>I have three select menus where the user selects a subject, year and season. However, I want it so that if the user selects the year '2019', the 'Fall' option will get disabled.</p>
  
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;select name="Subject"&gt;                  
      &lt;option value="Math"&gt;Math&lt;/option&gt;
      &lt;option value="Physics"&gt;Physics&lt;/option&gt;
      &lt;option value="Chemistry"&gt;Chemistry&lt;/option&gt;
      &lt;option value="Biology"&gt;Biology&lt;/option&gt;
  &lt;/select&gt;
  
  &lt;select name="Year"&gt;                  
      &lt;option value="2019"&gt;2019&lt;/option&gt;
      &lt;option value="2018"&gt;2018&lt;/option&gt;
      &lt;option value="2017"&gt;2017&lt;/option&gt;
      &lt;option value="2016"&gt;2016&lt;/option&gt;
  &lt;/select&gt;
  
  &lt;select name="Season"&gt;                  
      &lt;option value="Spring"&gt;Spring&lt;/option&gt;
      &lt;option value="Fall"&gt;Fall&lt;/option&gt;
  &lt;/select&gt;</code></pre>
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