You are deploying an application on App Engine that needs to integrate with an on-premises database. For security purposes, your on-premises database must not b...

You are deploying an application on App Engine that needs to integrate with an on-premises database. For security purposes, your on-premises database must not be accessible through the public internet. What should you do?

A. Deploy your application on App Engine standard environment and use App Engine firewall rules to limit access to the open on-premises database. B. Deploy your application on App Engine standard environment and use Cloud VPN to limit access to the on-premises database. C. Deploy your application on App Engine flexible environment and use App Engine firewall rules to limit access to the on-premises database. D. Deploy your application on App Engine flexible environment and use Cloud VPN to limit access to the on-premises database.