In my view, all alternatives contribute to the formation of opinion on some subject.
To get an opinion on a subject, first of all, you need to read and be informed. In this sense, research in the media (C), news (B) are the beginning, where you get integrated on the subject. After absorbing the initial knowledge, democratic debate on the subject can enrich their knowledge and it can be done through conversations with your parents (A), in political rallies (D), since politics is usually the place for talk about ideas. Finally, attending hearings and other civic events (E) also contribute, since in these locations you can watch specialists debating the subjetcs.