What does the term "anonymous" refer to?

The term "anonymous" is used to describe something or someone whose identity is not known or revealed. In the context of information or sources, an anonymous source is one that does not disclose their identity, often for reasons of confidentiality or privacy. This allows individuals to provide information without fear of repercussions or personal exposure.

In contrast, the other choices relate to identified or well-known entities. For example, "well-known" implies that a person's identity is public and recognized, while "a disclosed name" specifically indicates that the identity has been revealed. Similarly, "a documented identity" suggests that there is official or recognized information about the person. Therefore, "anonymous" clearly aligns with the concept of being unknown or undisclosed, affirming that the correct answer is indeed the identification of an unknown source.