robots.txt

Where does it go?

[mark1]

I know I know in the root.

I am confused. The site I am helping with has all the file under public_html dirctory. You go to the-site.com and all you see are the files in public_html. So should the robots.txt file should go

A) Beside the public_html dir and all disallowed dirs should be
disallow: /public_html/dir_name/
OR
B) Put the robots.txt file in public_html and
disallow: /dir_name/

Thanks again