You are writing a Compute Engine hosted application in project A that needs to securely authenticate to a Cloud Pub/Sub topic in project B.
What should you do?

A. Configure the instances with a service account owned by project B. Add the service account as a Cloud Pub/Sub publisher to project A. B. Configure the instances with a service account owned by project A. Add the service account as a publisher on the topic. C. Configure Application Default Credentials to use the private key of a service account owned by project B. Add the service account as a Cloud Pub/Sub publisher to project A. D. Configure Application Default Credentials to use the private key of a service account owned by project A. Add the service account as a publisher on the topic