Answer:
C. nmap & D. telnet
Explanation:
Why nmap?
nmap is a command that is used to determine which hosts are running and which services are being executed in such hosts. This is a well-known command among the hacking community to provide access to this type of information in order to grab information from open ports.
Why telnet?
Like nmap, telnet is used to examine which ports are opened and which ones are closed. Opened ports represent a breach in the network, leading to hackers accesing the information through this access point.