html5页面，代码如下，该引用的文件也引用了，点击下拉菜单就是没有反应
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Bootstrap</title>
<link rel="stylesheet" href="css/bootstrap.min.css">
<style>
.a {
height: 50px;
border: 1px solid #ccc;
background-color: #eee;
}
body {
margin: 50px;
}
</style>
</head>
<body>
<div class="dropdown">
<button class="btn btn-default" data-toggle="dropdown">
下拉菜单
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li><a href="#">a</a></li>
<li><a href="#">b</a></li>
<li><a href="#">c</a></li>
<li><a href="#">d</a></li>
</ul>
</div>
<script src="js/bootstrap.min.js"></script>
<script src="js/jquery-1.12.4.min.js"></script>
</body>
</html>