How can the established keyword in an ACL entry be used?
A. to permit only the returning TCP packets from an already existing TCP connection, and deny the initial TCP packet of a new session from an untrusted network
B. to permit both the initial TCP packet of a new session and the returning TCP packets from an existing TCP connection
C. to permit only the initial TCP packet of a new session
D. to change a router into a true stateful firewall controlling the access on a session-by-session basis