Validation Check

Hi

   In below questionaire i want if user clicks next then user should should select at least one option of answer

.

A.B.C.D.

of

Questions<%--Previous--%>PreviousNextSubmit<%--Next--%>

Using below script but not working

<script type="text/javascript">
        function MutExChkList(chk) {
            var chkList = chk.parentNode.parentNode.parentNode.parentNode;
            var chks = chkList.getElementsByTagName("input");
            for (var i = 0; i < chks.length; i++) {
                if (chks[i] != chk && chk.checked) {
                    chks[i].checked = false;
                }
            }
        }
    </script>

Thanks