Answer:
When actively reading a text, highlighting the main idea of each paragraph can help the reader to better understand the overall message of the text. This strategy can be especially helpful when the reader needs to summarize or analyze the text later on. By identifying the main idea of each paragraph, the reader can also begin to see how the different ideas in the text are connected to each other and how they contribute to the overall theme or argument. While titles, footnotes, citations, and minor details can also be important, highlighting the main ideas of each paragraph is a useful strategy for staying engaged with the text and gaining a deeper understanding of its content.
Therefore the answer is C. The main idea of each paragraph.