JSFiddle - React, Tailwind, and code Playground

HTML

<script>
    function validateForm(){
        if (!document.getElementById('v1').checked || !document.getElementById('v2').checked || !document.getElementById('v3').checked){
            alert('answer all questions please');
            return false;
        }
        return false;
}
</script>
<form name="form1" action="mark.php" method="post"> 
    <input type="radio" value="1" id="v1" name="v1"> 
    <input type="radio" value="1" id="v2" name="v2"> 
    <input type="radio" value="1" id="v3" name="v3"> 
    <input type="submit" onclick="return validateForm()" value="Send">
</form>