What components make up the main YAML file structure?

The correct components that make up the main YAML file structure are YAML keys and values. In YAML, data is structured in a way that uses key-value pairs to represent information. The keys serve as identifiers, while the values hold the data associated with those keys. This structure allows for a clear organization of data that is both human-readable and machine-parsable.

The other choices do not accurately represent the main components of YAML files. Regex expressions and rules are relevant in programming and data validation contexts but do not directly pertain to the YAML file structure itself. JSON syntax includes its own rules and formatting which are distinct from YAML, making it a different approach to data serialization. Plain text and images are forms of data but do not define the structure of YAML files, which specifically revolves around the usage of keys and their respective values.