I would say the best clear answer is D, because A is a little bit unclear but I would say the best answer is D.
Why?
Mesh Topology is expensive considering more links as compared to Ring topology.
Answer:
Remote access VPN
Explanation:
The solution that represents the majority of VPN's on the markets and is commonly referred to as a VPN appliance is the Remote access VPN
A remote access VPN is a type of VPN that works by creating a virtual channel (appliance ) between different devices for the purpose of exchanging data in an encrypted form. although this Tunnel passes through the public internet the Data exchanged are only accessible by the devices connected via the tunnel only .
The remote access VPN is mostly used to connect an employee to the company's network therefore it represent the majority of VPNs in the market.
Taking data and instructions from a user, processing the data as per instructions, and displaying or storing the processed data, are the four major functions of a computer. These functions are also known as the input function, process function, output function, and storage function, respectively.
