Undocumented changes should never be allowed by the Project Manager. He should ensure that whenever a change is requested, the impact on features and functions of the product (including that on the triple constraints) is documented with a change request. Only then should the change continue through integrated change control. Option A, value-added changes, describe changes in the scope that would provide benefits such as cost reduction. Option B, errors and omissions, could be both in project scope, which is the work required to complete the project, and the product scope, which refers to the features and functions of the deliverables. Option C, risk response, involves changes in the scope required to mitigate an identified risk. Option D, verbal undocumented changes, poses maximum potential threat to a project.