A penetration tester ran an Nmap scan on an Internet-facing network device with the -F option and found a few open ports. To further enumerate, the tester ran another scan using the following command:
nmap -O -A -sS -p- 100.100.100.50
Nmap returned that all 65,535 ports were filtered
Which of the following MOST likely occurred on the second scan?

A. A firewall or IPS blocked the scan.
B. The penetration tester used unsupported flags.
C. The edge network device was disconnected.
D. The scan returned ICMP echo replies.