NavBar菜单中的HTML/CSS下拉菜单

<nav class="navbar">
  <ul class="navbar-nav">
    <li class="nav-item">
      <a class="nav-link" href="#">Home</a>
    </li>
    <li class="nav-item dropdown">
      <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
        Services
      </a>
      <div class="dropdown-menu" aria-labelledby="navbarDropdown">
        <a class="dropdown-item" href="#">Service 1</a>
        <a class="dropdown-item" href="#">Service 2</a>
        <a class="dropdown-item" href="#">Service 3</a>
      </div>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="#">About</a>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="#">Contact</a>
    </li>
  </ul>
</nav>

.navbar {
  background-color: #f8f9fa;
  padding: 10px;
}

.navbar-nav {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-item {
  margin-right: 10px;
}

.nav-link {
  color: #333;
  text-decoration: none;
}

.dropdown-menu {
  display: none;
  position: absolute;
  background-color: #fff;
  padding: 10px;
}

.dropdown-item {
  display: block;
  padding: 5px;
  color: #333;
  text-decoration: none;
}

.nav-item:hover .dropdown-menu {
  display: block;
}