Final Answer:
No unit, or part thereof, may be awarded more than three unit awards, regardless of type (including Joint unit awards), for the same act or period of service (Option C).
Step-by-step explanation:
According to the question, the limit on the number of unit awards for the same act or period of service is three. This means that a unit or part of a unit cannot receive more than three unit awards, regardless of the type of award, including Joint unit awards. This restriction is in place to maintain a balance in recognizing and honoring units for their achievements and service without excessive repetition of awards for the same act or period of service.
Option C is the answer.