Which condition must be met to convert a lookup relationship to a master-detail relationship?

To convert a lookup relationship to a master-detail relationship, it is essential to remove any roll-up summary fields associated with that relationship. This is because roll-up summary fields are specifically tied to master-detail relationships, where the detail record (child) allows the parent record to summarize information, such as counting the child records or summing a numeric field.

If there are existing roll-up summary fields on the lookup relationship, it indicates a connection that is not compatible with the conversion process, as these fields would not function correctly within a lookup relationship framework. Therefore, removing any roll-up summary fields is a prerequisite for allowing the master-detail relationship to be established properly.

Other conditions mentioned in the alternatives may relate to different aspects of relationships in Salesforce but do not directly address the requirements for converting a lookup relationship to a master-detail relationship. For example, existing records with null values do not necessarily affect the relationship type conversion directly, and having no existing sharing rules is not a requirement for such a conversion. The lookup field being required can also be a factor, but it is not mandatory for the conversion itself, unlike the need to manage roll-up summary fields.