According to the PMBOK® Guide (Project Management Body of Knowledge), the process of obtaining seller responses, selecting a seller, and awarding a contract is known as Conduct Procurements.

Conduct Procurements (Option A): This is the execution phase of procurement management. Key activities during this process include advertising the procurement, holding bidder conferences, and—most importantly—receiving bids and proposals from prospective sellers. The outputs of this process include selected sellers and formal agreements (contracts).

Plan Procurement Management (Option B): This is the planning stage where the team decides what to buy, how to buy it, and identifies potential sellers. It involves creating the Procurement Management Plan and the Procurement Statement of Work (SOW), but it does not involve the actual receipt of bids.

Estimate Costs (Option C): This process belongs to the Project Cost Management knowledge area. It involves developing an approximation of the monetary resources needed to complete project work. While seller bids might be an input to refining these estimates, the act of receiving the bids itself happens in Conduct Procurements.

Control Budget (Note: " Determine Budget " or " Control Costs " ): In PMI terminology, Determine Budget aggregates the estimated costs of individual activities to establish a cost baseline. Control Costs is the monitoring and controlling process. Neither process is responsible for the administrative receipt of procurement bids.

In summary, the transition from planning to execution in procurement is marked by the Conduct Procurements process, where the project team actively engages the market to collect and evaluate seller responses.