int? maxResults what does the ? means in this statement
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/2699373/c-sharp-basic-question-what-is">C# - Basic question: What is ‘?’?</a>  </p>
</blockquote>



<p>I have found this statement in a function arguments.</p>

<pre><code>public static SyndicationFeed GetDataFeed(...... int? maxResults)
</code></pre>

<p>what does that means?</p>
