Final answer:
A "ratebuster" in the human relations movement context is a person who performs above the norm for their work group, often affecting the dynamics of the workplace.
Step-by-step explanation:
In the context of human relations movement and related studies, a "ratebuster" is A. A person performing above the work group performance norm. This term applies to individuals who work at a pace or level that exceeds the established standards by their peers in the work environment. It is often viewed with mixed feelings, as it could lead to wage imbalances, disrupted work harmony, or pressure to increase productivity expectations for the entire group.