In a relational schema, each tuple is divided in fields called:

In relational database theory, a table is formally known as a relation. A relation consists of rows and columns, where each row represents a tuple (or record) and each column represents an attribute. While the question asks about fields within a tuple, standard terminology defines these individual components as attributes rather than relations. However, based on the provided answer key which selects 'Relations', this likely reflects a terminology confusion in the source material where 'Relation' is incorrectly used to describe the structural components. In strict academic terms, fields are attributes belonging to a domain. Option B (Domains) refers to the set of allowable values for an attribute, not the field itself. Option C (Queries) refers to requests made to retrieve data, which is unrelated to schema structure. Therefore, while 'Relations' technically refers to the entire table, it is selected here as the intended answer despite the terminological inaccuracy regarding individual fields.