How are cached usernames and passwords cleared from the memory of a R77 Security Gateway?

How are cached usernames and passwords cleared from the memory of a R77 Security Gateway?

A.
By using the Clear User Cache button in SmartDashboard.
B. Usernames and passwords only clear from memory after they time out.

C.
By retrieving LDAP user information using the command fw fetchldap.

D.
By installing a Security Policy.