A top-to-bottom relationship among the items in a database is established by a A. Hierarchical schema B. Network schema C. Relational schema D. All of the above E. None of the above

The correct answer is: A. Hierarchical schema

A hierarchical schema is a type of database schema in which data is organized in a tree-like structure. Each item in the database has a parent item and can have multiple child items. This type of schema is often used for storing data that has a natural hierarchical structure, such as a company’s organizational chart or a family tree.

A network schema is a type of database schema in which data is organized in a network-like structure. Each item in the database can have multiple parents and multiple children. This type of schema is often used for storing data that has a complex relationship between items, such as a product catalog or a library’s catalog of books.

A relational schema is a type of database schema in which data is organized in a table-like structure. Each table contains a set of rows and columns. Each row represents an individual item in the database, and each column represents a different attribute of that item. This type of schema is often used for storing data that does not have a natural hierarchical or network structure, such as a customer database or a product inventory database.

Therefore, the only option that describes a top-to-bottom relationship among the items in a database is A. Hierarchical schema.