Final answer:
Contributing financially to a labor union is not considered an unfair labor practice (ULP) under the Wagner Act, which supports workers' rights and collective bargaining, while prohibiting employer interference with unions.
Step-by-step explanation:
The question asks which of the following is not considered an unfair labor practice (ULP) under the Wagner Act. Among the options provided, contributing financially to a labor union is not an unfair labor practice under the Wagner Act. The Wagner Act supports workers' rights and union activities, including the right to bargain collectively and the prohibition of employer practices that interfere with union activities.
A refusal to bargain with chosen employee representatives or any actions that restrain or coerce employees in the exercise of their rights are considered ULPs under the Wagner Act. However, a ten-day strike notification for the steel industry may be a reference to specific legal requirements or obligations outside the general provisions of the Wagner Act.