LPIC-2 Certified Linux Engineer (202-450) (#23)

Which of the following lines is valid in a configuration file in /etc/pam.d/?

auth required pam_unix.so try_first_pass nullok
auth try_first_pass nullok, require pam_unix.so
auth required:pam_unix.so(try_first_pass nullok)
auth pam_unix.so(required try_first_pass nullok)