The correct answer is setting up a Cloud Storage bucket as the log sink destination, as it is unnecessary for routing logs to Splunk. The other options are essential for this process: a Pub/Sub topic is required to send logs to Splunk, a log sink is necessary to route the selected logs to the destination, and the logging service account must have permissions to write to the Pub/Sub topic. For more details, refer to the documentation on setting up the logging export.