Edit in JSFiddle

$("#add").on('click', function () {
    var rows = 1;    
    var lastRow;
    lastRow = $('#experiance tr').last().clone().appendTo("#experiance");      
});

<form>
    <table border="1" id="experiance">
        <tr>
            <th>Sl No</th>
            <th>Language</th>
            <th>Experiance</th>
            <th>Proficient</th>
        </tr>
        <tr>
            <td> <input type="text" /> </td>
            <td> <input type="text" /></td>
            <td> <input type="text" /></td>
            <td>
                <select>
                     <option value = "1">Beginner</option>/>
                     <option value = "2">Itermediate</option>/> 
                     <option value = "3">advanced</option>/>
                </select> 
            </td>
        </tr>
    </table>
    <input id="add" type="button" value="Add New Row" />
</form>