You are doing IP spoofing while you scan your target. You find that the target has port 23 open.Anyway you are unable to connect. Why?

A.
A firewall is blocking port 23

B.
You cannot spoof + TCP

C.
You need an automated telnet tool

D.
The OS does not reply to telnet even if port 23 is open

Explanation:
The question is not telling you what state the port is being reported by the scanning utility, if the program used to conduct this is nmap, nmap will show you one of three states “open”, “closed”, or “filtered” a port can be in an “open” state yet filtered, usually by a stateful packet inspection filter (ie. Netfilter for linux, ipfilter for bsd). C and D to make any sense for this question, their bogus, and B, “You cannot spoof + TCP”, well you can spoof + TCP, so we strike that out.