How many broadcast domains are created if three hosts are connected to a Layer 2 switch in full- duplex mode?

Four broadcast domains would require a Layer 3 device or VLAN configuration - a basic Layer 2 switch with no VLANs cannot create 4 broadcast domains from 3 hosts.

Three broadcast domains would imply one per port, which is how collision domains work on a switch, not broadcast domains.

Zero broadcast domains is incorrect - at least one broadcast domain always exists in any active switched network segment.

A Layer 2 switch forwards broadcast frames out all ports except the source port, meaning all connected devices reside in one broadcast domain. Full-duplex mode affects collision domain behavior (each port is its own collision domain) but has no impact on broadcast domain segmentation. Only a Layer 3 device or VLANs can segment broadcast domains.