Which network technique separates broadcast domains?

The correct answer is routers because they are specifically designed to separate broadcast domains. In networking, a broadcast domain is a logical division that allows devices to communicate within the same segment. When a device sends a broadcast packet, routers prevent that packet from being forwarded to devices in other networks or segments, thus maintaining the integrity and efficiency of network communication.

While switches and bridges can operate at different layers of the OSI model and manage traffic within the same broadcast domain by forwarding Ethernet frames, they do not separate broadcast domains. Instead, switches can increase the number of collision domains but not the broadcast domains. Modems, on the other hand, are used to connect networks to the internet and do not separate broadcast domains. Routers, hence, serve the critical function of routing traffic between different networks while isolating and managing broadcasts efficiently.