Outcome specifications should be used when:

Comprehensive and Detailed Explanation (from CIPS L4M2 – Specification Types)

Outcome (or output) specifications define what outcome must be achieved, leaving suppliers freedom to decide how.

They are appropriate when multiple solutions can deliver the same performance.

Option C directly reflects this.

Options A, B, and D contradict the flexibility principle.

Relevant L4M2 references:

“Performance and outcome-based specifications”

“Encouraging innovation through output requirements”