SQL practice: Materialized Views: Caching a Query

Create a materialized view named branch_revenue holding branch_id, branch_name and total revenue (quantity times unit_price from order_items) for every branch that has orders.

Query the branch_revenue materialized view for branches with revenue above 400000. Show branch_name and revenue, ordered by revenue descending.

Create a unique index named branch_revenue_pk on branch_revenue over branch_id, so the view can later be refreshed concurrently.

Create a materialized view named product_sales holding product_id, product_name and total units sold, for products that have been sold at least once.

Which statement about materialized views is true?