How do unions affect wages for workers nationwide?

Question $6$ options:

A$)$

Union workers make more than all nonunion workers in the same industry.

B$)$

Union workers make more than nonunion workers when averaged across all private sector industries.

C$)$

Union workers in public sector jobs make more than private sector counterparts.

D$)$

Union workers make less than nonunion workers in the same industry.