Which of the following is NOT a network protocol?

The correct choice highlights that SQL is not a network protocol but rather a programming language used for managing and manipulating relational databases. SQL stands for Structured Query Language and is primarily utilized to create, read, update, and delete data in database systems. It facilitates the interaction between databases and applications, allowing for structured data management.

In contrast, the other options represent various protocols used for communication over networks. TCP/IP (Transmission Control Protocol/Internet Protocol) is the foundational suite of protocols that enable data transmission on the internet and other networks. DNS (Domain Name System) is responsible for translating human-readable domain names into IP addresses, enabling browsers to locate resources on the internet. DHCP (Dynamic Host Configuration Protocol) is used for dynamically assigning IP addresses to devices on a network, allowing them to communicate effectively.

Understanding the distinctions among these terms clarifies why SQL stands out as a non-protocol choice in the context of network communications.