The correct answer is B. Create a unique External ID field and use Data Loader.

Cloud Kicks is receiving shipment data from an external shipping system on a regular basis. To prevent duplicate Delivery records and update the correct existing records, the app builder should create a field such as Tracking Number on Delivery__c , mark it as External ID and Unique, then use Data Loader Upsert.

Salesforce documentation states that external IDs can be used when importing custom objects to prevent duplicate records. Salesforce Data Loader documentation also states that upsert combines insert and update: if a matching record exists, it updates it; otherwise, it creates a new record.

A is less appropriate because this is a recurring system migration/update scenario, and Data Loader with External ID is the stronger tool.

C is incomplete because matching only on Salesforce ID requires the external system to already store Salesforce record IDs.

D may help detect duplicates, but duplicate/matching rules do not provide the clean upsert mechanism needed to update the correct existing record.

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