Newspapers and other traditional media tend to include a variety of that represent conservative and liberal columnists, leaving the reader with a broader picture of what's happening in the world. a. stories b. viewpoints c. ads d. information

I'd go with viewpoints.

Usually we call those "viewpoint" articles by syndicated columnists "opinion" pieces or "op-eds."  "Op-ed" was newspaper shorthand for the page opposite the newspaper's editorials by its own staff.  On the page opposite, various other viewpoints from other writers would be featured.  Often enough people think of "op-ed" as shorthand for an "opinion editorial" -- which is a suitable definition of the term also.