Which of the following is used as an input to prepare a cost management plan?

Expert judgment is a tool and technique used in the Plan Cost Management process, not an input.

Lessons learned are part of organizational process assets, which may be referenced but are not the primary input described in the process.

Cost estimates are an output of the Estimate Costs process and are not yet available when the cost management plan is being prepared.

According to the PMBOK Guide, the Plan Cost Management process uses the project management plan as a key input because it contains the scope baseline and other subsidiary plans that inform how costs will be estimated and controlled. The project management plan defines the project approach, which directly shapes cost management decisions. Without this overarching plan, the cost management plan cannot be properly aligned to project objectives.