Choice "D" is correct. Some workers, for example cab drivers, must be paid at least minimum wage but need not be paid overtime. These are generally described as exempt workers.
Choice "b" is incorrect. If workers are within the overtime provisions, they also are within the minimum wage provisions.
Choice "a" is incorrect. Not all workers are subject to the minimum wage requirements. For example, farm workers need not be paid minimum wage.
Choice "c" is incorrect. The exemptions do not depend on a union contract.
