radioButton Checked

<!DOCTYPE html>
<html>
<head>
    <title></title>

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

</head>
<body>

    <form action="">


      <h1>Car</h1>
      <input type="radio" name="car" value="BMW" checked> Male<br>
      <input type="radio" name="car" value="Ferai"> Female<br>
      <input type="radio" name="car" value="Audi"> Other<br><br>


      <h1>Motor Cycle</h1>
      <input type="radio" name="motor" value="Honda" checked> Honda<br>
      <input type="radio" name="motor" value="Yahama"> Yahama<br>
      <input type="radio" name="motor" value="Suzuki"> Suzuki<br><br>


      <h1>Mobile</h1>
      <input type="radio" name="mobile" value="iPhone" checked> iPhone<br>
      <input type="radio" name="mobile" value="Xiomi"> Xiomi<br>
      <input type="radio" name="mobile" value="Samsung"> Samsung<br><br>


    </form>


    <script>
        var x =  document.querySelectorAll('input[type="radio"][name="car"]');


        x[1].checked=true;

        document.write(x.length);
        document.write(x[0].name);
    </script>

</body>
</html>