What do you conclude from the nmap results below?
Staring nmap V. 3.10ALPHA0 (www.insecure.org/map/)
(The 1592 ports scanned but not shown below are in state: closed)
Port State Service
21/tcp open ftp
25/tcp open smtp
80/tcp open http
443/tcp open https
Remote operating system guess: Too many signatures match the reliability guess the OS. Nmap
run completed – 1 IP address (1 host up) scanned in 91.66 seconds

A.
The system is a Windows Domain Controller.

B.
The system is not firewalled.

C.
The system is not running Linux or Solaris.

D.
The system is not properly patched.

Explanation:
There is no reports of any ports being filtered.