Step 1: Define the term "protocol" in the context of computing.
A protocol is a standard set of rules that allow electronic devices to communicate with each other. These rules include what data is communicated, how it's communicated, and how errors are handled.
Step 2: Analyze the other options.
(A) Resource Locator (like URL): An address for a resource on the internet, not a set of rules.
(B) Hypertext (like HTML): A system for displaying text that links to other text.
(D) Domain: A name that identifies a network or website on the internet.
The term that means "a set of rules" is a protocol. Examples include HTTP (Hypertext Transfer Protocol) and TCP/IP (Transmission Control Protocol/Internet Protocol).