Which of the following statements about the network shown in the figure is true?

The sub-interface of Router B cannot learn the MAC address of the sub-interface of Router A.

The sub-interface of Router A cannot learn the MAC address of the sub-interface of Router B.

The sub-interface numbers of Router A and Router B are different, so Router A and Router B cannot communicate with each other.

The host at 10.0.12.1 can ping the host at 10.0.12.2.