Final answer:
Switches are multiport devices that improve network efficiency by using packet switching to intelligently forward data only to the specific port leading to the destination device. Unlike switches, modems, gateways, and concentrators do not improve network efficiency in the same capacity.
Step-by-step explanation:
The multiport devices that improve network efficiency are Switches. Switches are networking devices that connect multiple devices together on a computer network, using packet switching to forward data to its destination. Unlike hubs, which broadcast the same data to all ports, switches are intelligent devices that learn the identity of the devices connected to each of its ports and forward data only to the specific port which leads to the destination device, greatly enhancing network efficiency and security.
Modems (Modulator-Demodulator) are devices that modulate an analog carrier signal to encode digital information and also demodulate such a signal to decode the transmitted information, but they do not improve efficiency in the same way switches do. Gateways are network nodes that connect two networks with different transmission protocols together. They can perform protocol conversion but mainly serve as a point of entry or exit from one network to another.