TopicDescriptionNetwork SystemA network operating system or NOS is a type of operating system that manages computer network resources such as data, and applications and ensures security. such as a router, switch, or firewall. A Network system firewall can be defined as a special type of network security device or a software program that monitors and filters incoming and outgoing network traffic based on a defined set of security rules. It acts as a barrier between internal private networks and external sources (such as the public Internet). Operating SystemAn Operating System can be defined as an interface between user and hardware. Some examples of operating systems include Apple macOS, Microsoft Windows, Google's Android OS, Linux Operating System, and Apple iOS. MemoryROM (read-only memory) is a non-volatile memory typeData stored in ROM cannot be electronically modified after the manufacture of the memory device. CommunicationE-mail is defined as the transmission of messages on the Internet. It is one of the most commonly used features over communications networks that may contain text, files, images, or other attachments. Therefore the correct matching code is A ? II, B ? III, C ? IV, D ? I.