Known as the Ping Service, ICMP Is A(n) __________ and Should

Multiple Choice

Known as the ping service, ICMP is a(n) __________ and should be ___________.

A)  essential feature, turned on to save money
B)  common method for hacker reconnaissance, turned off to prevent snooping 
C)  infrequently used hacker tool, turned off to prevent snooping
D)  common method for hacker reconnaissance, turned on to save money