Final answer:
Howard Zinn argues that the Progressive period did not bring real reform due to the lack of change in fundamental conditions for working people, such as low wages and harsh working conditions. One example that supports Zinn's argument is the continuation of these conditions for many laborers.
Step-by-step explanation:
Howard Zinn argues that the Progressive period did not usher in real reform because fundamental conditions did not change for masses of working people. One example that would support Zinn's argument is option D: The continuation of low wages and harsh working conditions for many laborers. Despite some positive changes such as the establishment of labor unions and improved working conditions, the overall conditions for working people did not significantly improve during the Progressive period. Zinn believes that true reform requires addressing the systemic issues that perpetuate inequality.