The correct answer is C. Create a master-detail relationship between the parent and child object with a roll-up summary field that filters on the status field.

A roll-up summary field is the recommended declarative solution when Salesforce needs to summarize child-record data on a parent record. Salesforce documentation states that roll-up summary fields calculate values from related records and are defined on the master side of a master-detail relationship.

In this scenario, Opportunity is the parent and Detailed_Sales__c is the child. The roll-up summary field can summarize sales metrics and use filter criteria so only child records where Status = Active are included.

Why others are incorrect:

A is incorrect because a third-party AppExchange app is unnecessary when native roll-up summary functionality meets the requirement.

B is incorrect because Apex is not recommended when a declarative feature can solve the requirement.

D is incorrect because lookup relationships do not support standard roll-up summary fields. Salesforce documentation states that lookup relationships are similar to master-detail relationships, except they do not support roll-up summary fields.

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