To accurately answer your question regarding how paragraph 4 refines the central idea, I would need access to the specific content of that paragraph from the article "Why Journalism Has A Gender Problem" by Corinne Segal. Since I don't have access to the article, I can't provide a definitive answer.
However, if you could summarize or provide the main points of paragraph 4, I could help you determine which option (a, b, c, or d) best fits how it refines the central idea.