answer is C

C: Materialized views are automatically and transparently maintained by Snowflake. A background service updates the materialized view after changes are made to the base table. This is more efficient and less error-prone than manually maintaining the equivalent of a materialized view at the application level. Materialized views are designed to improve query performance for workloads composed of common, repeated query patterns. However, materializing intermediate results incurs additional costs. As such, before creating any materialized views, you should consider whether the costs are offset by the savings from re-using these results frequently enough.

materialized view is automatically refreshed by a Snowflake managed warehouse.