Option A is the most direct and operationally efficient way to trigger the existing Lambda-based load into Amazon Redshift whenever a new CSV file is uploaded to Amazon S3. The key requirement is event-driven automation on ''new object created'' events, and the study material explicitly describes using Amazon EventBridge to react to S3 uploads by creating a rule on the default event bus and routing matching events to a target application.

Compared with queue-based designs (Options B and D), Option A reduces components: there is no need to manage an SQS queue, batching/visibility timeout behavior, or retry semantics at the consumer layer. This is especially appropriate because the files are small ( 5 MB) and the Lambda function is already implemented to perform the copy/load step. Using DMS (Option C) is not designed for ''S3 object arrival Lambda Redshift'' event triggering; it introduces unnecessary services and operational work for a simple file-ingestion trigger.