怎样让下面这个radio选择框如果选择另外一个，则另外一个自动隐去？

Question

<input type=radio name=a value=1 checked onclick="showAndHide(newvolume,newvolume2)">a
<input type=radio name=a value=2 onclick="showAndHide(newvolume2,newvolume)">b<br>
<span id="newvolume" style="visibility:hidden;">显示a</span><span id="newvolume2" style="visibility:hidden;">显示b</span>
<script language="javascript">
<!--
function showAndHide( e, e2 )
{
e.style.visibility = "visible";
e2.style.visibility = "hidden";
}
//-->
</script>

Answer 1

<span id="SA"><input type=radio name=a value=1 checked onclick="javascript:newvolume2.style.visibility=(this.checked?'visible':'hidden');document.all.SB.style.visibility='hidden'">a</span>
<span id="SB"><input type=radio name=a value=2 onclick="javascript:newvolume.style.visibility=(this.checked?'visible':'hidden');document.all.SA.style.visibility='hidden'">b</span><br>
<span id="newvolume" style="visibility:hidden;"><a onclick="document.all.SA.style.visibility='visible';newvolume.style.visibility='hidden'">显示a</span><span id="newvolume2" style="visibility:hidden;"><a onclick="document.all.SB.style.visibility='visible';newvolume2.style.visibility='hidden'">显示b</a></span>

Answer 2

比如:有A,B两个radio,那选择A的时候是要A隐藏还是B隐藏?