Answer: B

Internet Control Message Protocol - ICMP is a management
protocol and

messaging service provider for IP. Its messages are carried
as IP

datagrams.

ICMP is used in the following events:

Destination Unreachable - If a router cannot send an IP
packet any

further, it uses an ICMP echo to send a message back to the
sender

notifying it that the remote node is unreachable.

Buffer Full - If a routers memory buffer is full ICMP will
send out a

message to the originator.

Hops - Each IP datagram is assigned a path. This consists of
hops. If it

goes through the maximum number of hops, the packet is
discarded and the

discarding router sends an ICMP echo to the host.

Ping - Ping use ICMP echo message to check connectivity.