The correct answer is I and II, which are headings and subheadings.
Explanation:
Headings are used to identify in a short phrase what a section of a divided text is about, it helps the reader to recognize the main idea of each section.
Subheadings usually divide the text into small sections and the reason to do that is that this way it is easier for the reader to understand the text when they are scan reading. Subheadings give hints of the main idea for each section the text is divided into. Last, subheadings always appear within the text.