In the following figure, which would be true if the hub was replaced with a switch?

Currently, all of the computers are within one giant collision domain. Replacing the hub with a switch will create four separate potential collision domains. Switches create microsegmentation, which increases the number of collision domains and increases bandwidth. The number of collision domains would only decrease if you swapped a switch for a hub, thus creating one collision domain. The number of broadcast domains would be unaffected using either a switch or a hub unless a router was used for routing between VLANs.