Bootstrap 4 nested dropdown?

Question

What I am trying to do is if anyone click on arts then History sociology and geography submenu should show up. It should now appear when someone clicks on Arts.
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Answer 1

$(document).ready(function () {
    $("#type").change(function () {
        var val = $(this).val();
        if (val == "arts") {
            $("#type").html("historysociologygeography");
        } else if (val == "science") {
            $("#type").html("mathsphysics");
        }
    });
});

    --Select an Item--
    Arts
    Science