ROUTER!
On shared-media networks (i.e. hubs or pure ethernets), routers break up broadcast domains and bridges break up collision domains. Routers also break up collision domains. On switched networks, routers break up broadcast domains, and every switch port is its own separate collision domain.
No
Since a router does not forward broadcast messages it automatically splits up the broadcast domains for all clients connected to them.
router
A bridge typically creates separate collision domains within the same broadcast domain. If you take a bridge with 2 ports, each port connects to a LAN segment that is in its own collision domain. Therefore, for a 2 port bridge you will get 2 different collision domains.
NO
A broadcast domain is created any time you connect several clients together via a network connectivity device, such as a hub or switch or bridge. They would all be in the same broadcast domain for every client connected to them. Since a router does not forward broadcast messages, it creates different broadcast domains.
A Router
One of ways to do that is to use VLAN, but you need switch or router supporting. Also just single router without VLAN can separate networks isolating broadcast and collision domains. Some switches can limit broadcast domains too but they are rather expensive.
YES
Not only do bridges and switches separate collision domains but routers also perform this task.
VLAN