A master-detail relationship provides the required cascade-delete behavior. Supplier__c should be configured as the master and Supplier_Item__c as the detail. Salesforce explicitly states that when a master record is deleted, its related detail and subdetail records are also deleted. This ensures that terminating the Supplier relationship removes the dependent Supplier Item records automatically without additional Flow or Apex automation. An indirect lookup relationship is used primarily to relate external-object data to Salesforce records and does not provide the required ownership and cascade behavior. A hierarchical relationship is available only for relationships involving the User object. Many-to-many describes a data-model pattern normally implemented with a junction object and does not itself specify the required parent-child cascade. Master-detail therefore directly implements the stated lifecycle dependency.

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