Your application stores files on Cloud Storage by using the Standard Storage class. The application only requires access to files created in the last 30 days. You want to automatically save costs on files that are no longer accessed by the application. What should you do?
A. Create an object lifecycle on the storage bucket to change the storage class to Archive Storage for objects with an age over 30 days.
B. Create a cron job in Cloud Scheduler to call a Cloud Functions instance every day to delete files older than 30 days.
C. Create a retention policy on the storage bucket of 30 days, and lock the bucket by using a retention policy lock.
D. Enable object versioning on the storage bucket and add lifecycle rules to expire non-current versions after 30 days.
A provides a simple, automated, and cost-effective solution for your scenario.