Option A is essential as a log sink is required to route the selected logs to the necessary destination. Option C is crucial because the logging service account needs permissions to write to the Pub/Sub topic. Option D is necessary as a Pub/Sub topic is needed to send logs to Splunk. However, Option B is correct because a Cloud Storage bucket is not required for routing logs to Splunk. Reference: https://cloud.google.com/architecture/exporting-stackdriver-logging-for-splunk#set_up_the_logging_export