Final answer:
Topic sentences in a research essay are based on the subjects or topic areas into which the data is grouped.
Step-by-step explanation:
When outlining a research essay, the basis for topic sentences can be determined by the subjects or topic areas into which the data is grouped. Each topic sentence should represent a different main idea or point related to the research topic. For example, if the essay is about climate change, one topic sentence could focus on the impacts of rising temperatures, while another topic sentence could address the role of human activities.
The topic sentences should reflect the main points that will be discussed in each paragraph of the essay. They are typically determined before writing the outline, but can be modified as needed during the writing process.
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