Which of the following statements is true about a master-detail relationship?

A master-detail relationship is a special type of relationship that creates a tightly coupled connection between two objects in Salesforce. In this relationship, the master object controls certain behaviors of the detail object, and the detail object inherits certain properties from the master.

In the context of the options given, the statement that can be considered true is that you can convert a lookup relationship to a master-detail relationship only if all records have a value. This is correct because, for the conversion to take place, Salesforce requires that all records in the detail object must have a valid and existing master record. If there are any detail records without a corresponding master record, the conversion will not be allowed. This reinforces the importance of data integrity and ensures that the relationships between the records are maintained accurately.

Understanding the nuances of master-detail relationships helps in designing a robust data model, particularly when considering the implications of record ownership, cascading delete behaviors, and sharing settings. This kind of understanding is critical for effective use of Salesforce in managing data relationships.