An administrator has just configured vsftp and notices that she cannot follow symbolic links when connected to the FTP server. What is the most likely reason for this?

While follow_symlinks=no (or allow_symlinks=NO) in vsftpd.conf would prevent following symbolic links, it's typically set to 'yes' by default, and a chroot environment (B) is a more common default security measure that inherently restricts external symlinks.

If vsftpd is running in a chroot environment, symbolic links that point to files or directories outside of the user's jailed directory will not be resolvable or followable, due to the restricted filesystem view and security isolation.

vsftpd is almost always compiled with support for symbolic links, as it's a fundamental filesystem feature, making lack of compilation support highly unlikely.

If the user account were listed in /etc/security/ftpusers, the user would be completely denied FTP access, not just prevented from following symbolic links.