you can try,
$('div#3 div.c').eq(1).append('<div class="new">NEW</div>');
or
$('<div class="new">NEW</div>').appendTo($('div#4 .c:eq(1)'));
You can try:
$(data).appendTo($('#'+ id +' .c'));
For greater specificity, the index of any particular div.c can be used;
$(data).appendTo($('#'+ id +' .c:eq(2)')); // append to third `div.c`
UPDATE: for appendTo() just wrapped the target selector with $() and it works for me.
NOTE DO NOT USE ONLY A NUMERIC ID. IT ID is FORBIDDEN. FOR MORE READ
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