Final answer:
The topic in an expository text is identified by the heading, which groups related information, describes the sections of text, and provides clear transitions and outline of the content.
Therefore, B is correct.
Step-by-step explanation:
The topic in an expository text is identified by the heading. Headings serve as a guide for readers by grouping related information and providing a clear outline of the content. In a well-crafted expository text, headings and subheads are used to convey meaning, structure, and provide transitions between sections. They accurately describe the sections of text or media that follow, introducing the main idea or topic that each section will discuss. This function of headings helps readers to navigate through the text, predicting the information that will be presented under each section.
In contrast, captions accompany images or graphics to provide context, lists may present information in a bullet or numbered format without necessarily indicating the overall topic, and graphic aids such as infographics support the text by visually representing data or concepts. Between these options, the heading is specifically designed to identify and describe the topic of the content that follows.