A Product Backlog holds 900 items, many years old, and nobody can see the ordering. What is the most valuable action?

• ARefine every item so the Product Backlog is complete and ready.
• BRe-estimate everything to establish a reliable total.
• CDelete the items that will never be built, since a Product Backlog nobody can read is not transparent and the deletions cost nothing.
• DSplit it into several Product Backlogs so each area is manageable.