A company's application is deployed with a user-managed Service Account key. You want to use Google-recommended practice

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A company's application is deployed with a user-managed Service Account key. You want to use Google-recommended practices to rotate the key.
What should you do?

A. Open Cloud Shell and run gcloud iam service-accounts enable-auto-rotate --iam-account=IAM_ACCOUNT.
B. Open Cloud Shell and run gcloud iam service-accounts keys rotate --iam-account=IAM_ACCOUNT --key=NEW_KEY.
C. Create a new key, and use the new key in the application. Delete the old key from the Service Account.
D. Create a new key, and use the new key in the application. Store the old key on the system as a backup key.