Which of the following is an amount added to the overall project budget to cover unknown risks?

The correct answer is a management reserve. This amount is allocated to cover unforeseen risks that arise during the project lifecycle. Management reserves are not included in the baseline budget, as they are set aside specifically to address potential issues that cannot be anticipated at the beginning of a project. This allows project managers to have a buffer for unexpected expenses that fall outside the planned scope.

Contingency reserves are also related to risk management but are designated for identified risks that are known and have been assessed during the planning phase. They are generally calculated based on the specific risks identified and are part of the overall project budget.

Overhead costs refer to ongoing business expenses not directly tied to the production of goods or services, such as utilities and administrative salaries. They do not specifically relate to project risks.

Fixed costs encompass expenses that do not change regardless of production levels, such as rent or salaries. These costs are predictable and not used for managing risks in a project setting. Thus, management reserves stand out as the correct choice for addressing unknown risks in project budgeting.