Which of the following technologies are considered metalanguages?

The correct choice identifies Standard Generalized Markup Language (SGML) and Extensible Markup Language (XML) as metalanguages. A metalanguage is a language used to describe, define, or manipulate other languages, particularly markup languages.

SGML is indeed a meta-language that defines the structure of documents by establishing rules on how to create markup languages, thus serving as a framework for defining document information. XML, built on the foundation provided by SGML, is designed to store and transport data while allowing users to define their own custom markup languages. Both SGML and XML allow for the creation of other languages that follow a similar structure but cater to specific needs, making them essential tools in the realm of document processing and data interchange.

In contrast, HTML and CSS are not considered metalanguages; rather, they are specific markup languages used to define the structure and presentation of web pages. JavaScript and PHP are programming languages that focus on logic, functionality, and creating behavior for web applications, not on defining other languages. Similarly, Python and Ruby are high-level programming languages used for a wide range of programming tasks and applications, thus also not fitting the definition of a metalanguage.