Under osha guidelines, which example is not an employer responsibility

Governments sometimes erect barriers to trade other than tariffs and quotas. which of the following is not an example of this type of trade barrier? a. a requirement that the employees of domestic firms that engage in foreign trade pay income taxes b. restrictions on imports for national security reasons c. a requirement that imports meet health and safety requirements d. a requirement that the u.s. government buy military uniforms only from u.s. manufacturers