Final answer:
The yellow-dog contract, which prevented employees from joining or assisting in organizing unions, is indeed true. These contracts were a method used by employers to combat unions, until legislation such as the Wagner Act prohibited such practices.
Step-by-step explanation:
The statement that the yellow-dog contract guaranteed that employees would neither join a union nor assist in organizing one is true. Employers used these contracts to suppress unions by making employment contingent upon the worker's agreement not to join a union. This practice was one of several anti-union strategies employed by businesses during the early 20th century amidst a tense environment between labor and management.
The National Labor Relations Act (Wagner Act) of 1935 later prohibited such contracts by guaranteeing workers the right to join unions and bargain collectively, but the Taft-Hartley Act of 1947 introduced new restrictions on unions, although it did not reinstate the yellow-dog contract.