You Want to Send and Consume Cloud Pub/Sub Messages from Your

You want to send and consume Cloud Pub/Sub messages from your App Engine application. The Cloud Pub/Sub API is currently disabled. You will use a service account to authenticate your application to the API. You want to make sure your application can use Cloud Pub/Sub. What should you do?

A) Enable the Cloud Pub/Sub API in the API Library on the GCP Console.
B) Rely on the automatic enablement of the Cloud Pub/Sub API when the Service Account accesses it.
C) Use Deployment Manager to deploy your application. Rely on the automatic enablement of all APIs used by the application being deployed.
D) Grant the App Engine Default service account the role of Cloud Pub/Sub Admin. Have your application enable the API on the first connection to Cloud Pub/Sub.