Some economists claim that unions reduce economic efficiency by:

A) providing a voice mechanism for workers.
B) insisting that promotions be based on ability rather than seniority.
C) imposing restrictions on the kinds of jobs workers may perform.
D) increasing worker turnover.

Unions often negotiate restrictions on the types of jobs workers can perform, such as limiting the number of tasks an employee can do in a given role or dictating certain qualifications for particular positions. This can limit the flexibility of the workforce, making it more difficult for firms to adapt to changing circumstances and reducing overall economic efficiency. The other options do not necessarily reduce economic efficiency, but may have different impacts on the labor market.