The two considerations that should be made are: The Star records are all required to have an existing value in their Galaxy field. This is a prerequisite for converting a lookup relationship to a master-detail relationship. A lookup relationship is an optional relationship that links two objects together, but does not enforce referential integrity or cascade delete. A master-detail relationship is a required relationship that links two objects together and enforces referential integrity and cascade delete. To convert a lookup relationship to a master-detail relationship, all child records must have a value in their lookup field that references an existing parent record. The Galaxy object has fewer than two existing master-detail relationships. This is another prerequisite for converting a lookup relationship to a master-detail relationship. An object can have up to two master-detail relationships with other objects and can act as both the parent and child in different relationships. To convert a lookup relationship to a master-detail relationship, the parent object must have fewer than two existing master-detail relationships with other objects. The Galaxy object is required to contain existing roll-up summary fields is not a valid consideration, as it is not related to converting a lookup relationship to a master-detail relationship.