The correct answer is D.
OBJ-5.7: If the lights are steady on a network interface card (NIC), it indicates that there is no network activity. If it is blinking, this indicates that data is passing over the NIC to the network. Even if there were an incorrect TCP/IP configuration or intermittent connectivity, there would be blinking lights to indicate transmission attempts. Since this is a wired network connection, it cannot be a low RF signal as that is a wireless network problem.