Which type of keys links to multiple rows in another entity?

The correct choice is foreign keys. Foreign keys are used in database design to create a link between two tables. Specifically, a foreign key in one table refers to the primary key in another table, establishing a relationship that allows for the representation of a one-to-many relationship. This means that a single entry in the primary table can be associated with multiple entries in the linked table.

For instance, consider a scenario where you have a "Customers" table and an "Orders" table. A customer can place several orders, so the "Orders" table will contain a foreign key that points to the customer's primary key. This allows for the tracking of all orders made by each customer.

In contrast, type keys and unique keys serve different purposes. Type keys define a specific category or type within a data structure, while unique keys ensure that a particular field is unique across a set of records but do not inherently create relationships between tables. Array keys, which pertain to data structures that allow collections of items, do not pertain to the relational database context of linking tables.