Which of the following best describes a natural language?

A natural language is specifically defined as a language that has evolved naturally through use in human communication. It is the type of language that is spoken, written, or signed by humans and is often characterized by its inherent complexity, nuances, grammar, and vocabulary that develop over time within cultures.

Natural languages include commonly spoken languages such as English, Spanish, Mandarin, and hundreds of others. These languages are used for interpersonal communication and have evolved organically, unlike artificial or formal languages which are carefully constructed for specific purposes, such as programming languages, markup languages, or computational languages.

The other options identify different types of languages that serve distinct purposes, such as programming languages designed for instructing computers or markup languages used for formatting text in documents. However, these do not fulfill the definition of natural languages, which exclusively relate to human communication and expression.