ปัญหาเรื่อง ข้อสอบ ผมจะแก้ไข่ข้อสอบ ทำยังไงคับ ทำไม่ได้

<form action="update_pretest.php" method="post" name="form1" id="form2">

          <?
$host="localhost";
$username="root";
$password="root";
$db="photosynthesis_db";
$tb="testing";
mysql_connect( $host,$username,$password) or die ("ติดต่อกับฐานข้อมูล Mysql ไม่ได้ ");
mysql_select_db($db) or die("เลือกฐานข้อมูลไม่ได้");
mysql_query("SET NAMES TIS-620");

$sql="Select * From $tb ";
$db_query=mysql_query($sql);
$i=0;
while($result=mysql_fetch_array($db_query))
{
$i++;
?>
          <table width="100%" border="0" align="center">
            <tr>
              <td width="6%"><div align="left"><?PHP echo"$i"; ?></div></td>
              <td colspan="2"><input name="id[<?=$i;?>]" type="hidden" value="<?=$result["id"];?>" />
                <input name="question" type="text" size="60" value="<?=$result["question"];?>"/></td>
            </tr>
            <tr>
              <td colspan="3" height="17"></td>
            </tr>
            <tr>
              <td colspan="2">&nbsp;</td>
              <td><input name="c<?=$i;?>" type="radio" value="1" />
                ก.
               <input name="c1" type="text" size="60" value="<?=$result["c1"];?>"/> </td>
              </tr>
            <tr>
              <td colspan="2">&nbsp;</td>
              <td><input type="radio" name="c<?=$i;?>" value="2" />
                ข.
                <input name="c2" type="text" size="60" value="<?=$result["c2"];?>"/></td>
              </tr>
            <tr>
              <td colspan="2">&nbsp;</td>
              <td><input type="radio" name="c<?=$i;?>" value="3" />
                ค.
                <input name="c3" type="text" size="60" value="<?=$result["c3"];?>"/></td>
              </tr>
            <tr>
              <td colspan="2">&nbsp;</td>
              <td><input type="radio" name="c<?=$i;?>" value="4" />
                ง.
                <input name="" type="text" size="60" value="<?=$result["c4"];?>"/>
                <input name="answer[<?=$i;?>]" type="hidden" value="<?=$result["answer"];?>" /></td>
              </tr>
          </table>
          <br />
          <?
}
mysql_close();
?>
          <div align="center">
            <input name="member_id3" type="hidden" id="member_id3" value="<?php echo $dbarr['member_id'] ; ?>" />
            <input type="submit" name="Submit2" value="เปลี่ยนแปลง" style="display:block" />
          </div>
        </form>

<?PHP
include("../config.inc.php") ;
mysql_select_db($db) ;
$question = $_POST['question'];
$c1= $_POST['c1'];
$c2= $_POST['c2'];
$c3= $_POST['c3'];
$c4= $_POST['c4'];

	    $sql[0] = "update testing set question='$question'";
		  $sql[1] = "update testing set c1='$c1' ";
		    $sql[2] = "update testing set c2='$c2' ";
			  $sql[3] = "update testing set c3='$c3' ";
			    $sql[4] = "update testing set c4='$c4'";
		
	
       for($i=0;$i<5;$i++) {
    $result = mysql_query($sql[$i]) or die("Err program");
       }
?>