Final answer:
Hubs forward all incoming data frames to all ports without making any decisions based on addresses. The correct answer is d. Nothing; hubs forward all frames on all ports.
Step-by-step explanation:
Hubs are devices used in networking to connect multiple computers or other network devices together. When it comes to forwarding decisions, hubs do not use any type of address to determine where to send data. Instead, they operate at the physical layer of the OSI model and simply repeat any incoming data frames to all other ports, regardless of the destination of the frames.
Therefore, the correct answer to the question is d. Nothing; hubs forward all frames on all ports. Hubs are considered to be unintelligent devices in comparison to switches, which do make forwarding decisions based on MAC addresses, and routers, which use IP addresses.