QT += widgets
SOURCES += main.cpp
QMAKE_PROJECT_DEPTH = 0

#include <QtWidgets>

class MainWindow : public QMainWindow {
public:
    MainWindow(QWidget *parent = nullptr) : QMainWindow{parent} {
        a.setText("A");
        b.setText("B");
        c.setText("C");
        d.setText("D");
        a.setChecked(true);
        c.setChecked(true);
        mainLayout.addWidget(&a);
        mainLayout.addWidget(&b);
        scrollLayout.addWidget(&c);
        scrollLayout.addWidget(&d);
        scrollWidget.setLayout(&scrollLayout);
        scrollArea.setWidget(&scrollWidget);
        mainLayout.addWidget(&scrollArea);
        central.setLayout(&mainLayout);
        setCentralWidget(&central);
    };
private:
    QRadioButton a;
    QRadioButton b;
    QRadioButton c;
    QRadioButton d;
    QWidget central;
    QVBoxLayout mainLayout;
    QScrollArea scrollArea;
    QWidget scrollWidget;
    QVBoxLayout scrollLayout;
};

int main(int argc, char *argv[]) {
    QApplication a(argc, argv);
    MainWindow w;
    w.setWindowTitle("Test");
    w.show();
    return a.exec();
}