A company wants to incorporate a third-party web service to set the Address fields when...

The requirement is to perform a callout when a record is inserted. Because Salesforce prohibits synchronous callouts after DML operations in the same transaction, this must be handled asynchronously.

Queueable Apex (Option C) is the optimal choice for this integration. When an Account is inserted, a trigger captures the ID and enqueues a Queueable job. Queueable is superior to Future methods (Option D) because it supports complex data types (not just primitives), allows for job chaining, and provides a Job ID that can be used for monitoring via AsyncApexJob.

Before-Save Flows (Option A) cannot directly perform callouts, and while they can trigger asynchronous paths, the programmatic control offered by a Trigger-to-Queueable pattern is more robust for complex third-party integrations. Batch Apex (Option B) is designed for bulk processing of existing records and is "overkill" for a real-time, record-by-record trigger requirement. By using a Trigger with Queueable, the developer ensures the address validation happens nearly in real-time without blocking the user's initial save transaction or hitting concurrent request limits.