The document discusses linguistic choice systems, specifically the mood system in language grammar. It notes that the mood system involves choices between indicative, imperative, declarative, interrogative, WH-interrogative, and non-WH interrogative moods. Within the indicative mood, there is a further choice between declarative and interrogative. Interrogative clauses can then be either WH-interrogative or non-WH interrogative. The imperative mood also allows for a choice between exclusive and inclusive forms.