After Passively Scanning the Network of Department of Defense (DoD)

After passively scanning the network of Department of Defense (DoD) , you switch over to active scanning to identify live hosts on their network. DoD is a large organization and should respond to any number of scans. You start an ICMP ping sweep by sending an IP packet to the broadcast address. Only five hosts respond to your ICMP pings; definitely not the number of hosts you were expecting. Why did this ping sweep only produce a few responses?

A) Only IBM AS/400 will reply to this scan
B) Only Windows systems will reply to this scan
C) A switched network will not respond to packets sent to the broadcast address
D) Only Unix and Unix-like systems will reply to this scan