Final answer:
The correct answer is option A. A signal phrase is a phrase, clause, or sentence that introduces a quotation from another source. It helps provide context and avoid plagiarism.
Step-by-step explanation:
A signal phrase is a phrase, clause, or sentence that introduces a quotation. It is used to inform readers that the words or ideas that follow come from another source. Signal phrases often contain a verb that indicates the tone or intention of the author. For example, phrases like 'argues,' 'states,' or 'suggests' can be used as signal phrases.
Signal phrases serve to give readers enough context to understand the quotation. They also help to avoid plagiarism by properly attributing the source of the quoted material. When using signal phrases, it is important to use correct punctuation, such as quotation marks, to separate the quotation from your own words and ideas.
It is important to note that a signal phrase is not a form of plagiarism, but rather a way to properly attribute and introduce a quotation. Therefore, option A) A phrase, clause, or sentence that introduces a quotation—also called a 'lead-in,' is the correct option.