Iron Triangles Have Been Replaced by Issue Networks for Which

Iron triangles have been replaced by issue networks for which of the following reasons?

A) The increase in corporate-sponsored interest groups made one corner of the iron triangle too powerful.
B) Because interest groups no longer have the kinds of influence they once had,public opinion as gleaned through polls has taken their place.
C) Issue networks consist of large numbers of individuals who are specialized in different fields and can provide Congress with needed information that the members of the iron triangle could not.
D) Increasing numbers of small,highly specialized groups have made one corner of the iron triangle harder to fill with a steady occupant.