The correct answer is D) biography.
A biography is an expository text.
In literary terms, when we are writing an expository text, it means that you want to expose information of any kind. The expository text goes directly to do an exposition of facts, information, characters or situations. What you are trying to do is to inform your readers. In this case, a biography is an expository text in that you expose the life, studies, accomplishments and other details of an individual.