Force specific checkbox selection

Forgive me for my ignorance, but I am just learning. I am using a specific javascript template for a checkbox selection. Found here

I am trying to force a specific checkbox selection, meaning no matter what the user selects, a specific checkbox is always the box selected. I have tried a few things and have not found any luck. Any help is appreciated, thanks!

<form class="ac-custom ac-radio ac-circle" autocomplete="off">
                <h2>Question</h2>
                <ul>
                    <li><input id="r5" name="r2" type="radio"><label for="r5">Selection 1</label></li>
                    <li><input id="r6" name="r2" type="radio"><label for="r6">Selection 2</label></li>
                    <li><input id="r7" name="r2" type="radio"><label for="r7">Selection 3</label></li>
                    <li><input id="r8" name="r2" type="radio"><label for="r8">Selection 4</label></li>
                </ul>
            </form>