The correct answer is B) they have decreased union membership.
The have right-to-work laws affected union membership in that they have decreased union membership.
Right to work laws helped workers in that this legislation prohibits companies to reject workers if they were not part of a union. Previously, many employers required workers to be part of a union. Paying union dues was not anymore a condition to be hired. The Right to Work legislation respected the right that workers have to join or not, any kind of union.