Public opinion refers to the collective views and attitudes of the people on various issues of national interest. It enables a government to find out what the public thinks about its activities, policies, and programs. By knowing the public opinion, the government can determine what policies or actions are necessary and appropriate to meet the needs and aspirations of the people. Public opinion also helps the government to gauge the level of support or opposition to its policies, as well as to identify areas of concern or dissatisfaction among the citizens. Therefore, the correct option is "find out what the public thinks about its activities."