Answer:
The correct answer is letter "D": peer to peer.
Step-by-step explanation:
Peer to Peer (P2P) networks are constituted by computers connected through the internet. Anybody with a computer internet access can connect to another computer within the same network and share files with no need for a central server granting access. The biggest disadvantage of this type of network is that as there is no central server, file sharing and back up are not controlled.