Which Attack Type May Be Indicated by Unsolicited ACKs Directed

Multiple Choice

Which attack type may be indicated by unsolicited ACKs directed toward an unused portion of a network's IP address space?

A) A smurf attack against a host located elsewhere, spoofing the unused IP space
B) a SYN flood attack against that IP address space
C) IP backscatter from an attack located elsewhere, spoofing your unused IP space
D) an ICMP flood attack against that IP address space