Hi Lionel,
unfortunately, it would be much more complex if you need to randomize the question or answer order because the only way to determine which answer to mark as also correct would be to use a find function to search for a string that is unique to that question and answer combo. If you absolutely need to use this on a randomized quiz, then take a look at the :contains selector.
If you’re not randomizing, then this becomes much simpler. I’m not sure what you mean by Post ID 275 unless you mean that is the post ID of the question – which isn’t needed.
Using $("#qq275").val ="1";
would be the 27th question on the page, 5th answer for that question.
Please let me know what your particular use case would be (IE, need randomized questions or not) and I’ll help best I can. HD Quiz was never meant to be able to have multiple correct answers, but worst case scenario I can release an update that will help us accomplish this.