To set the response to a single choice question, you can use the code below.
Note: the answers start at index 0, so the first answer in your list will be 0, the second 1 etc.
Best practice is to take the code of the answer and subtract 1.
Be sure to add the next auto click.
function pageReady(){
// where 0 is the first code, 1 is the second code etc.
$(".cRadio").eq(0).prop("checked",true).trigger("change");
setTimeout(function() {
$('.main-next-button').click();
}, seconds * 100);
}
Setting a singel response like this is only useful if you are setting the answer in a way that might not support the Survey Builder functionality to set answers in hidden questions found here.