Jquery序列化不会在嵌套div中选择一个select标记

So i have this form

所以我有这个表格

<form>
    <div>
        <span class="form_t">I Want To Trade In  
            <span id="trade_target"></span> 
        </span>
        <span class="form_t">With</span>

        <div class="selecting">
            <select>
                <option>A Mac</option>
                <option>An Iphone</option>  
            </select>
        </div>
    </div>

    <table id="tradein_table">
        <tr>
            <td class="textside">My contact Info</td>
        </tr>
        <tr>
            <td class="textside">Mobile Number</td>
            <td class="inputside"><input type="text" name="Mobile" id="t_mobile"/></td>
        </tr>
        <tr>
            <td class="textside">First Name</td>
            <td class="inputside"><input type="text" id="t_first" name="Fname"/></td>
        </tr>
        <tr>    
            <td class="textside">Last Name</td>
            <td class="inputside"><input type="text" id="t_last" name="Lname"/></td>
        </tr>   
        <tr>    
            <td class="textside">Email</td>
            <td class="inputside"><input type="text" id="t_email" name="Email"/></td>
        </tr>
        <tr>    
            <td class="textside">Company</td>
            <td class="inputside"><input id="t_company" type="text" name="Company"/>
        </td>               </tr>
    </table>

    <div class="submit_div">
        <input class="submit_form" type="submit" name="Submit" value="Submit" />
    </div>  
</form>
<form>
    <d