According to the PMBOK® Guide, the Determine Budget process involves aggregating the estimated costs of individual activities or work packages to establish an authorized cost baseline. To do this accurately, the project manager must review specific project documents that provide the necessary data and context for those costs.

Basis of Estimates, Cost Estimates, Project Schedule, and Risk Register (Choice B): These are all primary Inputs to the Determine Budget process:

Cost Estimates: These provide the direct monetary requirements for each activity within a work package.

Basis of Estimates: This document provides the supporting detail behind the cost estimates, explaining how they were derived and what assumptions were made (e.g., current exchange rates, labor categories).

Project Schedule: The budget must be time-phased. The schedule contains the planned start and finish dates for activities, which determines when the funds will be expended.

Risk Register: This is reviewed to determine the necessary Contingency Reserves. Identified risks and their planned responses have associated costs that must be factored into the total budget.

Choice A: While Contracts and Procurement Documents are inputs, " Requirements Documentation " is a more indirect input. Choice B is more comprehensive regarding the core data needed to build the mathematical baseline.

Choice B: The Business Case and Project Charter are higher-level documents usually used during project initiation. While they provide the " ceiling " for the budget, they do not provide the granular data required to determine the detailed budget during the planning phase.

Choice D: The Scope Baseline is a critical input, but the Resource Management Plan and Activity List are typically used to create the cost estimates in the previous process (Estimate Costs). By the time you are determining the budget, you are using the outputs of those earlier steps.

By aggregating these specific documents, the project manager creates the Cost Baseline, which is the approved version of the time-phased project budget, excluding any management reserves.