Here's why:
* Subheadings are smaller headings that break down a larger topic into smaller, more manageable sections. They act as signposts, clearly indicating the main idea of each section.
Let's look at why the other options aren't the best fit:
* Paragraphs contain the actual information, but they don't always clearly state the main idea.
* Photographs, diagrams, and captions provide visual information and context, but they don't usually summarize the main ideas of a text.
In summary, subheadings are the most effective text feature for organizing information by stating the main ideas.