After discovering a second sun in the solar system, Ursa Major Solar wants to change...

The correct answer is A. Existing reports created under the Sun__c with Planet__c report type made by Salesforce will be unusable, but not deleted.

When a relationship is changed from master-detail to lookup, the available standard report types can change. Salesforce documentation notes that converting a lookup relationship to master-detail or vice versa can make existing custom reports unusable because of differences in available standard report types.

B is incorrect because roll-up summary fields are not automatically deleted from reports as part of the conversion. In fact, Salesforce states that a master-detail relationship cannot be converted to lookup while roll-up summary fields exist on the master object.

C is incorrect because roll-up summary fields do not remain and simply stop updating.

D is incorrect because the reports are not deleted; they become unusable.

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