Answer: Refer the student to a text or agree to reach out after making considerable research to confirm the answer to the question.
Explanation: Unexpected questions are inevitable after presentation. Most times, presenters prepare for questions related to their subject of discourse and forget to prepare for worst scenario - Having an unexpected question being thrown at them. They're many ways to deal with such situations but first the most ideal is to admit to having little or no knowledge of the answer, which is followed with an assurance to reach out to the student after making research on the question. This goes to show that Sarah is smart and also willing to increase her knowledge of the things she doesn't know.