HTTP (Hypertext Transfer Protocol), DHCP (Dynamic Host Configuration Protocol), and DNS (Domain Name System) are all widely used protocols in the internet. However, the correct answer is option 'D' - None of the mentioned.

HTTP (Hypertext Transfer Protocol)
- HTTP is the protocol used for transmitting hypertext over the internet. It is responsible for the communication between web servers and web browsers.
- It is used to request and receive HTML pages, images, videos, and other web resources from web servers.
- HTTP operates on top of TCP/IP (Transmission Control Protocol/Internet Protocol) and uses port 80 for communication.

DHCP (Dynamic Host Configuration Protocol)
- DHCP is a network protocol used to automatically assign IP addresses and other network configuration parameters to devices on a network.
- It allows devices to connect to a network and obtain a unique IP address without manual configuration.
- DHCP operates on the client-server model, where a DHCP server allocates IP addresses to client devices.
- It is commonly used in home and enterprise networks to simplify the management of IP addresses.

DNS (Domain Name System)
- DNS is a protocol used to translate human-readable domain names (e.g., www.example.com) into IP addresses (e.g., 192.168.0.1).
- It acts as a distributed database that stores and retrieves information about domain names and their associated IP addresses.
- DNS enables users to access websites using easy-to-remember domain names instead of numerical IP addresses.
- It plays a crucial role in the functioning of the internet by providing the mapping between domain names and IP addresses.

None of the mentioned
- This option implies that all the protocols mentioned (HTTP, DHCP, and DNS) are used in the internet.
- It is incorrect because all three protocols are indeed used extensively in internet communications.
- The correct answer should be option 'D' - None of the mentioned.