请教一个单选框的问题，急！

Question

<input type="radio" id="r_d"  onclick="change()" >
<SCRIPT ID=clientEventHandlersJS LANGUAGE=javascript>
<!--
function change() {
if (r_d.checked==true){
r_d.checked= false;}
else{
r_d.checked= true;}
}
-->
</SCRIPT>

Answer 1

<input type=radio name=aa onmouseup="meizz = window.event.srcElement; if(checked)setTimeout('meizz.checked =! meizz.checked')">
<input type=radio name=aa onmouseup="meizz = window.event.srcElement; if(checked)setTimeout('meizz.checked =! meizz.checked')">
<input type=radio name=aa onmouseup="meizz = window.event.srcElement; if(checked)setTimeout('meizz.checked =! meizz.checked')">

Answer 2

<script>
cstatus=true;
</script>
<input name="a" type="radio" value="" checked onClick="if(cstatus){this.checked=false;cstatus=false}else{this.checked=true;cstatus=true}">

Answer 3

<input type=radio  onclick="(checked)?(checked=false):(checked=true)">