The correct answer is D. Reliable expert
Explanation:
A reliable expert is a professional in a field with enough knowledge and experience to provide a realistic and reliable opinion about a specific topic. For example, Albert Einstein is a reliable expert in the field of physics due to his experience and knowledge in this area. Additionally, in texts, the words of reliable experts are quoted to support the ideas of the author of the text. For example, you can quote Albert Einstein in an essay about physics or the theory of relativity. Thus, a person with credentials such as knowledge or experience that can be quoted in an essay is a reliable expert.
