Which statement about management reserve is true?

Management reserve is an amount of money or time set aside to address unforeseen risks and uncertainties that may arise in the course of a project. It is particularly associated with "known unknowns," which are risks that are acknowledged but not yet quantified. This reserve provides a financial buffer that enables project managers to handle unexpected issues without derailing the project's budget or timeline.

The other options speak to different aspects of project management. Documented risks, for example, are typically managed through contingency reserves rather than management reserves, as they involve risks that have already been identified and planned for. Ensuring resource availability pertains more to resource management than to the concept of management reserves. The notion of a calculated buffer of time is also more closely related to contingency reserves for known risks rather than the broader scope of management reserves, which specifically address unexpected challenges that arise.