What is a true statement regarding a master-detail relationship?

In a master-detail relationship, one object acts as the master, controlling certain behaviors of the detail object. A key aspect of this relationship is the presence of roll-up summary fields, which aggregate data from the detail records into the master record. Because roll-up summary fields rely on the details being linked as a master-detail relationship, if there are existing roll-up summary fields set up on the master record, you cannot convert that master-detail relationship to another type of relationship. Therefore, option A is correct, as it highlights that the presence of a roll-up summary field prevents the conversion of a master-detail relationship to a lookup relationship or any other type of relationship.

The other choices convey different dynamics of relationships in Salesforce. Option B refers to the sharing settings that change when converting a lookup to a master-detail, which is a true statement but not pertinent to the question about converting from master-detail. Option C proposes that a lookup can be converted to a master detail with existing null values, which is misleading as such records must adhere to specific data criteria, and option D addresses user experience in the interface but does not pertain directly to the nature of master-detail relationship conversions. These details serve to clarify the nuances of Salesforce relationships and ensure a comprehensive understanding of the topic