Which of the following is a language used for content provided by a web server to a web client?

FTP (File Transfer Protocol) is a network protocol for transferring files between systems, not a language for describing web content.

TCP (Transmission Control Protocol) is a transport-layer protocol that provides reliable data delivery; it operates below the application layer and has no role in defining content structure.

HTTP (HyperText Transfer Protocol) is the application-layer protocol used to request and deliver web content, not the language used to write that content.

HTML is a markup language that defines the structure and presentation of web page content. When a web server responds to a client request, it delivers HTML documents that the browser interprets and renders. HTML is the actual content language, distinct from HTTP which is only the communication protocol used to transport that content.