I am in 12th science If i fail in board exam then can I reapeat it ?

Hello dear student,
Greetings
Yes you can of course repeat.
you can give 12th board again  but only as a private candidate. It will not effect your academics  .You can DOWNLOAD form from cbse original web site if you are cbse student or from state board official web site , in that in public portal you go and then in left side find form and click and download your private candidate form.fill it as instructions are given and wit a xerox of original marksheet with you principal attested send through speed post.
if cant find form then go to cyber caffe from there you can get it.
all the best