Answer:
(C) Many businesses hire trainees at or near the minimum wage but must reward trained workers by keeping their pay levels above the pay level of trainees.
Step-by-step explanation:
From the context, it is given that only a small portion of the population who are workers will directly affect by the raise. But the raise can indirectly affect the other proportion of the population as well. Most of then people who are working as trainees are getting the minimum wages as compared to the trained workers.
As a result of the rise, the wages of the trainees might be equal to that of the TRAINED workers. But now many companies have to increase the wages of the trained people in order to make sure that the trained people get more wages than the trainees.
And if it is right or true, then the rise will affect not only a small proportion of workers but also the trained workers whose wages must be above the trainees.
Thus, option (C) weakens the argument.