$4.$ What is meant by generalized forwarding $($as opposed to destination$-$based forwarding$)$ in a router or switch?A$)$ The decision about which output port to forward a packet to can be made based on the link$-$type of the outgoing port $($e$.$g$.,$ Ethernet versus WiFi$).$b$)$ In addition to performing forwarding, the device can generalize its services, also performing hop$-$by$-$hop reliable data transfer and per$-$hop congestion control.C$)$ Any of several actions $($including drop $($block$),$ forward to a given interface, or duplicate$-$and$-$forward$)$ can be made based on the contents of one or more packet header fields.D$)$ None of the other answers is a correct definition of generalized forwarding.