Conditionally render another component based on selectOneMenu value

Question

This is my h:selectOneMenu part where dropdown click show 3 values (A,B & C) on UI (we have domainList method in bean containing A,B, C):

<h:form id="MainForm">
    <h:panelGrid columns="1">
        <h:selectOneMenu id="domainList" value="#{bean.domain}" listener="#{bean.changeDomainValue}">
            <f:selectItem itemLabel="#{msg.abc }"/>
            <f:selectItems value="#{bean.dMap.entrySet()}"
                           var="entry" itemLabel="#{entry.key}" itemValue="#{entry.value}"/>
            <f:ajax event="change" render="??????"/>
        </h:selectOneMenu>
    </h:panelGrid>

This is my concern where if I select Value="C" from dropdown list I need to add two checkbox in the existing form (an extra field ):

    <h:panelGrid columns="2">
        <h:outputLabel value="#{msg.box1}"></h:outputLabel>
        <h:selectBooleanCheckbox value="#{bean.chkBox1}"></h:selectBooleanCheckbox>
    </h:panelGrid>

    <h:panelGrid columns="2">

    <h:outputLabel value="#{msg.box2} :"></h:outputLabel>
    <h:selectBooleanCheckbox value="#{bean.chkBox2}"></h:selectBooleanCheckbox>
    </h:panelGrid>
</h:form>

Here is my Bean.java:

private void changeDomainValue(ValueChangeEvent e) {
    if (e.getNewValue() == "C") {
        this.chkBox1 = "true";
        this.chkBox2 = "true";
    } else
        this.chkBox1 = "false";
    this.chkBox2 = "false";
    //return false;
}

Question: what to add on render property so these two checkboxes will populate only if i select domainList= "c"?