802.1X provides port-based Network Access Control (NAC). Ports remain in a blocked state until a device authenticates (usually with RADIUS). This is ideal for public or semi-public areas where ports should not be
"always on."
A). Port security restricts by MAC addresses but does not authenticate users.
C). MAC filtering is easily spoofed and weaker than 802.1X.
D). ACLs filter traffic but do not enforce port-based authentication.
References (CompTIA Network+ N10-009):
Domain: Network Security - NAC, 802.1X authentication, port-based security.