Final answer:
Client hosts joining a multicast group are assigned shared IP addresses, which are used by all hosts in the group to receive multicast communications efficiently.
Step-by-step explanation:
When client hosts join a multicast group, they are assigned shared IP addresses. This means that the same IP address is used by multiple hosts that wish to participate in the same multicast session or group. Multicast IP addresses are allocated from a specific range that has been set aside for that purpose (224.0.0.0 to 239.255.255.255 in IPv4). In contrast to unicast communication, where each device on a network has a unique IP address, multicast allows efficient delivery of information to multiple recipients using a single multicast group address.