Answer:
D. transition from one paragraph to the next.
In academic writing, signal phrases are used to introduce a piece of evidence or a quotation from a source. The purpose of these phrases is to provide context and to help the reader understand how the evidence relates to the writer's argument. Signal phrases may include an author's name, source, or title, and they can help avoid plagiarism by crediting the original source of the information.
However, the primary purpose of signal phrases is to help with the organization and flow of the writing. They are often used as transitions between paragraphs, introducing new ideas or evidence and connecting them to the previous discussion. By using signal phrases, writers can create a clear and logical structure that helps the reader follow their argument.