Final answer:
In a relational database table, each row is called a tuple, which represents one data item consisting of multiple fields corresponding to the table's attributes. Therefore correct answer is option D.
Step-by-step explanation:
In a relational database, a tuple, often termed a record, constitutes each row within a table. Functioning as an implicitly structured data unit, a tuple encapsulates a singular instance in the table. Comprising various fields, each aligning with a table column or attribute, these tuples collectively define the table's content. The tables themselves are denoted as relations in the context of relational databases. Each tuple signifies a distinct occurrence of the entity type delineated by the table.
This fundamental relational model underscores the organization and representation of data, emphasizing the structured and interconnected nature of information in the database system.