次の例で、最初のドロップダウン メニューの一部が別のドロップダウン メニューによって非表示になるのはなぜですか。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="description" content="">
<meta name="author" content="">
<!-- Note there is no responsive meta tag here -->
<link rel="shortcut icon" href="../../docs-assets/ico/favicon.png">
<title>MarkerDB</title>
<!-- Bootstrap core CSS -->
<link rel="stylesheet" type="text/css" href="//netdna.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" >
<link rel="stylesheet" type="text/css" href=//cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.6.2/css/bootstrap-select.min.css>
<!-- Custom styles for this template -->
<link href="http://getbootstrap.com/examples/non-responsive/non-responsive.css" rel="stylesheet">
</head>
<body>
<div class="container">
<form class="form-inline" action="/between/" method="get">
<div class="input-group">
<span class="input-group-addon">TestA</span>
<select name="tests" class="selectpicker form-control" data-live-search="true" title="Plese select a test ...">
<option selected value="1">Test1</option>
<option selected value="2">Test2</option>
</select>
<span class="input-group-btn">
<button class="btn btn-default" type="submit">Search!</button>
</span>
</div>
</form>
<hr>
<form class="form-horizontal" action="/compare/" method="get" role="form">
<div class="input-group">
<span class="input-group-addon">TestB:</span>
<select name='cultnames' class="selectpicker show-menu-arrow form-control" multiple data-max-options="2" data-live-search="true">
<option value="Test3">Test3</option>
<option value="Test4">Test4</option>
</select>
<span class="input-group-btn">
<button class="btn btn-default" type="submit">Search!</button>
</span>
</div>
</form>
<hr>
<HR>
</div> <!-- /container -->
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js"></script>
<script type="text/javascript" src="//netdna.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
<script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.6.2/js/bootstrap-select.min.js"></script>
<script>
$('.selectpicker').selectpicker();
</script>
</body>
</html>