<div class="dropdown">
  <button class="dropdown-button">下拉菜单</button>
  <ul class="dropdown-menu">
    <li><a href="#">选项1</a></li>
    <li><a href="#">选项2</a></li>
    <li><a href="#">选项3</a></li>
  </ul>
</div>

.dropdown-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  padding: 0;
  margin: 0;
  background-color: #fff;
  border: 1px solid #ccc;
}

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

.dropdown-menu li {
  display: block;
  padding: 10px;
}

.dropdown-menu li:hover {
  background-color: #f2f2f2;
}