如何在这段代码中使用Ajax？

</tr>

<tr>
 <td><input type="radio" name="ans" id='ans_2' value="2" /> <? echo " "; echo $ans2 = $ques['ans_2'];?></td>
</tr>
<tr></tr>
<tr>
 <td><input type="radio" name="ans" id='ans_3' value="3"  /> <? echo " "; echo $ans3 = $ques['ans_3'];?></td>
</tr> 
<tr></tr>
<tr>
 <td><input type="radio" name="ans" id='ans_4' value="4" /> <? echo " "; echo $ans4 = $ques['ans_4'];?></td>
</tr>
</tr>

<tr>
 <td><input type="radio" name="