The "Hollywood Ten" were a. The ten top-grossing films in Hollywood b. The ten most important American films according to the American Film Institute c. The ten filmmakers who were imprisoned for refusing to cooperate at Congressional hearings investigating alleged Communist infiltration of Hollywood d. The ten filmmakers who named names of Communist members and sympathizers

Option C: The ten filmmakers who were imprisoned for refusing to cooperate at Congressional hearings investigating alleged Communist infiltration of Hollywood

Explanation:

The hollywood ten were simply ten filmmakers in the United States, who were mostly screen writers. They were sentenced to prison for contempt of congress. The HUAC hearing that made Hollywood to investigate Communist infiltration of the film industry. They decided by refusing to cooperate with the committee because some of the film makers either from the conviction that the committee's action's infringed on their constitutional rights or simply due to the fact that they had been communist party memebers.

b) to encourage free trade