I have a check box list and when i select 1 item and then i want the opposite option to not be selectable eg. if i select "Fit to work on heights" then "Unfit to work on heights" should be disbaled from selection.

 Below is my CheckboxList that i am populating from code behind: 

<div class="card">
    <div class="card-header"><asp:Label ID="lblExamOutcomeRecommendation"  Visible="true" Font-Bold="true" runat="server" Text="Recommendations :"></asp:Label></div>
    <div class="card-body"> 
         <asp:CheckBoxList ID="ChkExamOutcomeRecommendations" RepeatLayout="Table" Width="100%" RepeatDirection="Horizontal" RepeatColumns="2" runat="server"></asp:CheckBoxList>
    </div>
    <div class="card-footer">
        <asp:CustomValidator ID="CustomValidator2" ErrorMessage="Please select at least one item." CssClass="alert alert-danger" Width="100%" ClientValidationFunction="ValidateCheckBoxList2" runat="server" />
    </div>
</div>