Checkboxes below checked checkbox can't be checked

Hello I am having problems on fixing this. I have 4 checkboxes wherein only 1 checkbox can get checked at a time. Meaning that if the second box is currently checked and I ticked the first box, then the second box's check should be removed.

Here's my javascript

var a = $('.8kfth').val();
        $(':checkbox').on('click', this, function(){
            if ($('.8kfirstchk').prop('checked')==true && $('.8kfth').val()=="one")
            {
                $('.8ksecondchk, .8kthirdchk, .8kfourthchk').prop('checked', false);
                $('.ft-identifier').html('').append('8-K with 425');
            }
            else if ($('.8ksecondchk').prop('checked')==true && $('.8kfth').val()=="one")
            {
                $('.8kfirstchk, .8kthirdchk, .8kfourthchk').prop('checked', false);
                $('.ft-identifier').html('').append('8-K with DEFA14A or DFAN14A');
            }
            else if ($('.8kthirdchk').prop('checked')==true && $('.8kfth').val()=="one")
            {
                $('.8kfirstchk, .8ksecondchk, .8kfourthchk').prop('checked', false);
                $('.ft-identifier').html('').append('8-K with SC TO-C');
            }
            else if ($('.8kfourthchk').prop('checked')==true && $('.8kfth').val()=="one")
            {
                $('.8kfirstchk, .8ksecondchk, .8kthirdchk').prop('checked', false);
                $('.ft-identifier').html('').append('8-K with SC TO-C');
            }
        });

And here's the html

<TABLE style="LINE-HEIGHT: 13pt; BORDER-COLLAPSE: collapse" cellSpacing=0 cellPadding=0 width="100%" border=0>

<TR vAlign=bottom>
    <TD NOWRAP WIDTH="1%" STYLE="text-align: left; vertical-align: middle"><FONT size=2 face="Times New Roman"><input type="checkbox" class="8kfirstchk">&nbsp;&nbsp;</FONT></TD>
    <TD WIDTH="99%" STYLE="text-align: left; vertical-align: middle"><FONT face="Times New Roman" size=2>425</FONT></TD></TR>
<TR>
    <TD NOWRAP WIDTH="1%" STYLE="text-align: left; vertical-align: middle"><FONT size=2 face="Times New Roman">&nbsp;&nbsp;</FONT></TD>
    <TD WIDTH="99%" STYLE="text-align: left; vertical-align: middle"></TD></TR>
<TR vAlign=bottom>
    <TD NOWRAP WIDTH="1%" STYLE="text-align: left; vertical-align: middle"><FONT size=2 face="Times New Roman"><input type="checkbox" class="8ksecondchk"></FONT></TD>
    <TD WIDTH="99%" STYLE="text-align: left; vertical-align: middle"><FONT face="Times New Roman" size=2>PANDA</FONT></TD></TR>
<TR>
    <TD NOWRAP WIDTH="1%" STYLE="text-align: left; vertical-align: middle"><FONT size=2 face="Times New Roman">&nbsp;&nbsp;</FONT></TD>
    <TD WIDTH="99%" STYLE="text-align: left; vertical-align: middle"></TD></TR>
<TR vAlign=bottom>
    <TD NOWRAP WIDTH="1%" STYLE="text-align: left; vertical-align: middle"><FONT size=2 face="Times New Roman"><input type="checkbox"  class="8kthirdchk"></FONT></TD>
    <TD WIDTH="99%" STYLE="text-align: left; vertical-align: middle"><FONT face="Times New Roman" size=2>SCIENCE TO SCIENCE</FONT></TD></TR>
<TR>
    <TD NOWRAP WIDTH="1%" STYLE="text-align: left; vertical-align: middle"><FONT size=2 face="Times New Roman">&nbsp;&nbsp;</FONT></TD>
    <TD WIDTH="99%" STYLE="text-align: left; vertical-align: middle"></TD></TR>
<TR vAlign=bottom>
    <TD NOWRAP WIDTH="1%" STYLE="text-align: left; vertical-align: middle"><FONT size=2 face="Times New Roman"><input type="checkbox"  class="8kfourthchk"></FONT></TD>
    <TD WIDTH="99%" STYLE="text-align: left; vertical-align: middle"><FONT face="Times New Roman" size=2>SCIENCE TO SCIENCE</FONT></TD></TR></TABLE>