Which of the following is prohibited by the National Labor Relations Act (NLRA)?

The National Labor Relations Act (NLRA) aims to protect the rights of employees in their relationships with employers and to encourage collective bargaining. One of the key provisions of the NLRA is the protection of employees' rights to engage in collective discussion and negotiation regarding their wages, working conditions, and other employment-related matters. Therefore, prohibiting discussion about wages is a violation of the NLRA because it restricts the employees’ ability to communicate freely about their work conditions, which is fundamental to their right to organize and advocate for better terms of employment.

Encouraging employees to unionize, promoting workplace democracy, and providing job training for unions are all activities that support or enhance collective bargaining and employees' rights, and as such, are not prohibited by the NLRA. Instead, these actions are encouraged as they contribute to a fair work environment where employees can freely express their opinions and work together towards their collective interests.