Final answer:
The auditor should exclude Measure C from the performance scorecard because it cannot evaluate individual performance and the task is too easy, failing to drive performance improvement.
Step-by-step explanation:
The auditor should recommend excluding performance measures that cannot be distinctly linked to an individual's performance or that do not offer a significant challenge to the individual. From the options provided, Measure C, indicating both individual performances cannot be evaluated and the task is easy, should be excluded from the performance scorecard. Measures should be able to assess individual contributions effectively and be challenging enough to drive performance improvements.