You can simply give the same name to the respective radio groups to achieve this like:
<tr>
<td>1</td>
<td>
<input type="radio" name="rbtnAttendance1" />Present
<input type="radio" name="rbtnAttendance1" />Absent
</td>
</tr>
<tr>
<td>2</td>
<td>
<input type="radio" name="rbtnAttendance2" />Present
<input type="radio" name="rbtnAttendance2" />Absent
</td>
</tr>
This way you can only select one option from the radio buttons with same name.