wanted to know what might be the problem with my dropdown button in index.php

I tried different methods but still the dropdown options didn't show.

Here is my code

<li class="nav-item dropdown">
   <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-hospup="true">
   categories
   </a>
   <div class="dropdown-menu" aria-labelledby="navbarDropdown">
      <a class="dropdown-item" href="#">Critical infrastructure security</a>
      <a class="dropdown-item" href="#">Application security</a>
      <div class="dropdown-divider"></div>
      <a class="dropdown-item" href="#">Network securitys</a>
   </div>
</li>