How should a customer reliably deliver Stackdriver logs from GCP to their on-premises SIEM system?

How should a customer reliably deliver Stackdriver logs from GCP to their on-premises SIEM system?

A. Send all logs to the SIEM system via an existing protocol such as syslog. B. Configure every project to export all their logs to a common BigQuery DataSet, which will be queried by the SIEM system. C. Configure Organizational Log Sinks to export logs to a Cloud Pub/Sub Topic, which will be sent to the SIEM via Dataflow. D. Build a connector for the SIEM to query for all logs in real time from the GCP RESTful JSON APIs.