The correct answers are B. Use a roll-up summary field on the Park record and C. Use a master-detail relationship between the Park and Trail objects.

Northern Trail Outfitters wants the total number of Trails displayed on the Park record without code. In Salesforce, a standard roll-up summary field can count related child records, but it requires a master-detail relationship between the parent and child objects. Salesforce documentation confirms that roll-up summary fields calculate values from related records, and this is the correct declarative feature for this requirement.

A is incorrect because a formula field cannot count child records. D is incorrect because standard roll-up summary fields do not work on ordinary lookup relationships.

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