You work for a financial services company that wants to use fully managed database services. Traffic volume for your consumer services products has increased annually at a constant rate with occasional spikes around holidays. You frequently need to upgrade the capacity of your database. You want to use Cloud Spanner and include an automated method to increase your hardware capacity to support a higher level of concurrency. What should you do?

A. Use linear scaling to implement the Autoscaler-based architecture B. Use direct scaling to implement the Autoscaler-based architecture. C. Upgrade the Cloud Spanner instance on a periodic basis during the scheduled maintenance window. D. Set up alerts that are triggered when Cloud Spanner utilization metrics breach the threshold, and then schedule an upgrade during the scheduled maintenance window.