Final answer:
The ICMPv6 message that is sent when the IPv6 hop limit field of a packet is decremented to zero and the packet cannot be forwarded is time exceeded.option b.
Step-by-step explanation:
The ICMPv6 message that is sent when the IPv6 hop limit field of a packet is decremented to zero and the packet cannot be forwarded is time exceeded. This message is used to inform the source node that the packet has exceeded the maximum number of hops allowed and cannot reach its destination. The time exceeded message includes a copy of the original packet's IPv6 header and the first eight bytes of the original payload to help with troubleshooting.
The ICMPv6 message that is sent when the IPv6 hop limit field of a packet is decremented to zero and the packet cannot be forwarded is time exceeded. This message is part of the Internet Control Message Protocol for IPv6 (ICMPv6) suite, which is used by network devices to communicate error messages and operational information. When a packet traverses from one router to another, its hop limit is decremented by 1. If the hop limit reaches zero before reaching its destination, to prevent the packet from looping indefinitely in the network, it is discarded and the time exceeded message is sent back to the source of the packet indicating that the packet could not be delivered due to the hop limit being exceeded.