jQuery根据条件不显示下一个下拉列表

MY 逻辑是创建一个图书馆管理系统，其中它首先询问学生班级名称，而不是如果选择了中级（在数据库中为 1），然后显示中间组，否则如果选择了 BS 而不是显示 BS 部门。

<?php 
require '/include/connect.inc.php';
require '/include/core.inc.php';
?>
<script type="text/javascript" src="include/JS/jquery-1.11.2.min.js"></script>
<script type="text/javascript" src="include/JS/jQuery.js"></script>
<style>tr.Department_Options{ display: none; }</style>
<div class="articles">
    <form method="POST" action="#">
        <table align="center">
<tr><th><label for="ChoosedClassID">Class : </label></th><td><select  name="ChoosedClassID" id="ChoosedClassID"><option  disabled selected>Select Class :</option><?php 
$query="SELECT ClassID,ClassName from class ORDER BY ClassName ASC";
$query_run=mysqli_query($connect,$query) OR die(mysqli_error($connect));
while($catch=mysqli_fetch_array($query_run)) {
    $ClassName=$catch['ClassName'];
    $ClassID=$catch['ClassID']; ?>
  <option value="<?php echo $ClassID;?>"><?php echo $ClassName; ?></option> 
 <?php } ?></select><br></td></tr>
<tr id="tr_A" class="Department_Options"><th><label for="id_A">Choose Your Group : </label></th><td><select  name="InterGroupID" id="InterGroupID"><option  disabled selected>Intermediate Group :</option><?php
$query="SELECT DID,DepartmentName from department WHERE ClassID=1 ORDER BY DepartmentName ASC";
$query_run=mysqli_query($connect,$query) OR die(mysqli_error($connect));
while($catch=mysqli_fetch_array($query_run)) {
    $DepartmentName=$catch['DepartmentName'];
    $DID=$catch['DID']; ?>
  <option value="<?php echo $DID;?>"><?php echo $DepartmentName; ?></option> 
 <?php } ?></select><br></td></tr>
<tr id="tr_B" class="Department_Options"><th><label for="id_B">Choose Department : </label></th><td><select  name="DepartmentName" id="DepartmentName"><option  disabled selected>BS Department Name</option><?php
$query="SELECT DID,DepartmentName from department WHERE ClassID=2 ORDER BY DepartmentName ASC";
$query_run=mysqli_query($connect,$query) OR die(mysqli_error($connect));
while($catch=mysqli_fetch_array($query_run)) {
    $DepartmentName=$catch['DepartmentName'];
    $DID=$catch['DID']; ?>
  <option value="<?php echo $DID;?>"><?php echo $DepartmentName; ?></option> 
 <?php } ?></select><br></td></tr>
</table>                  
</form>
</div>

jQuery.js文件

$(document).ready(function(){
    $('#ChoosedClassID').on('change', function() {         
        $('tr.Department_Options').hide();
        $('#tr_' + $(this).val() ).show();
    });
});

根据上面的代码，当我选择BS，中间时，下一个下拉菜单Meny不会出现。

我想要的是出现下拉菜单，当我从中选择某个值时，它应该询问学生图书馆编号，然后我想进行插入查询。