The root directory of a disk should be placed
The top directory in a file system. The root directory is provided by the operating system and has a special name; for example, in DOS systems the root directory is called \. The root directory is sometimes referred to simply as the root.
reference - https://www.webopedia.com/TERM/R/root_directory.html
so Option B is right option
following link is Kvs_Pgt_Question Paper...