Concept:A primary key is a field used to uniquely identify each record in a database table.Explanation:In the given figure, count the fields that are marked or defined as primary keys.The primary key fields shown are customerID, orderID, and productID.These keys are present in the respective tables and each one uniquely identifies its records.No other field in the diagram is designated as a primary key.Since there are three such fields, the total number of primary keys in the figure is 3.Answer:A. 3