Answer:
c. the mix of workers used in the production process was more experienced than the normal mix.
Explanation:
In the case when there is an unfavorable labor rate variance so that means the workers that are for the production process would be more experienced as compared to the normal mix of the workers . In other words, when the normal mix workers are less as compared to the mix of workers used do there should be unfavorable labor rate variance
hence, the option c is correct