title: WordPress: How to display only one category
body: <p>In my design I show the category of the post in the home page. 
  The problem is when I add more that one category in a post. 
  How can I make so that it will display only one category. </p>
  
  <p>Example: I have 3 categories A, B and C. 
  I add a post in categories A and B. 
  In the home page is displayed ... <em>Post title</em> in category A, B. 
  I want the output to be ... <em>Post title</em> in category A. </p>
  
  <p>For the category I use get_the_category_list</p>