Which of the following is a type of relationship in a relational database ?

In a relational database, relationships define how data in one table connects to data in another. There are three fundamental types of relationships supported by relational database models: one-to-one, where a single record in Table A relates to only one record in Table B; one-to-many, which is the most common type where a single record in Table A can relate to multiple records in Table B; and many-to-many, where multiple records in Table A can relate to multiple records in Table B. Since options A, B, and C all represent valid relationship types used to structure data effectively in relational systems like SQL databases, the correct choice must include all of them. Therefore, 'All of the above' is the accurate answer as it encompasses every valid relationship type listed in the other options.