$query2="SELECT de FROM dd2" ;
$resultg2 = mysqli_query($con, $query2);

$query4="SELECT de FROM dd4" ;
$resultg4 = mysqli_query($con, $query4);

$query6="SELECT de FROM dd6" ;
$resultg6 = mysqli_query($con, $query6);

$query10="SELECT de FROM dd10" ;
$resultg10 = mysqli_query($con, $query10);

    <script>
        function check(tnved)
        {
            if (tnved == 2 )
			{//alert("2");
			document.getElementById("answer1").action="ru/tnved2.php";}
			              
			if (tnved == 4 )
			{//alert("4");
			 document.getElementById("answer1").action="ru/tnved4.php";}
			if (tnved == 6 )
			{//alert("6");
			 document.getElementById("answer1").action="ru/tnved6.php";}
			if (tnved == 10 )
			{//alert("10");
			 document.getElementById("answer1").action="ru/tnved10.php";}
            }
    </script>

                            <span lang="ru"><input class="radio" type="radio" name="tnved"  onclick="check(this.value)" value="2"required><div class="radiobut"></div> 2 </span>   
                        </div>
                       	<div class="check">
                            <span lang="ru" class="robo"><input id="a-opt" class="radio radio-btn" type="radio" name="tnved" onclick="check(this.value)" value="4" required><div class="radiobut"></div> 4 </span>
                           </div>
								<div class="check">
                            <span lang="ru" class="robo"><input id="a-opt" class="radio radio-btn" type="radio" name="tnved" onclick="check(this.value)" value="6" required><div class="radiobut"></div> 6 </span>
                           </div>
								<div class="check">
                            <span lang="ru" class="robo"><input id="a-opt" class="radio radio-btn" type="radio" name="tnved" onclick="check(this.value)" value="10" required><div class="radiobut"></div> 10 </span>
                          </div>
			 	</span>
						<br> <br> <br>
						  <span lang="ru"><p><span>Шаг 2 - </span> Выберите товар по коду ТН ВЭД</p></span>
					   <span lang="ru">
						<select name="kodtnved" id="kodtnved" >
					      
						  <?php while ($row15 = mysqli_fetch_array($resultg6)):; ?> 
                          <option> <?php echo $row15[0];?> </option> 
						  <?php endwhile;?>
					  </select>	</span>