The correct answer is C (productivity = output/input) because, within the NCMA Contract Management Body of Knowledge (CMBOK), productivity is fundamentally defined as the ratio of outputs produced to the inputs used to produce them. This formula provides a clear and quantifiable measure of efficiency in utilizing resources such as labor, materials, time, and capital.

Output refers to the goods or services delivered, such as completed tasks, manufactured units, or services rendered under a contract. Input includes the resources consumed to achieve that output, including labor hours, costs, and materials. By dividing output by input, contract managers can assess how effectively resources are being used to generate results.

This metric is essential in contract management for evaluating performance efficiency, cost-effectiveness, and operational improvement opportunities. Higher productivity indicates better utilization of resources, while lower productivity may signal inefficiencies that require corrective action.

Option A and B incorrectly associate productivity with risk and reward, which are unrelated concepts. Option D (output + input) does not represent a meaningful performance ratio.

CMBOK emphasizes productivity measurement as part of management competencies, enabling contract managers to monitor performance, control costs, and improve overall contract outcomes.