One way writers narrow the focus of their writing is by eliminating unnecessary subtopics. When a writer is working on a piece of writing, they may initially have a broad topic or idea in mind. However, to make their writing more focused and coherent, they need to narrow down their scope by identifying and eliminating any subtopics or details that are not directly relevant to their main point or argument. This helps to streamline the writing and prevent it from becoming too scattered or unfocused. By removing unnecessary subtopics, writers can ensure that their message or argument is clear and concise, making their writing more effective.