The author of the passage refers to The Dynamics of Folklore primarily in order to:
suggest that there are some signs that women folk performers are gaining increased critical attention in the field of folklore
Look at the lines –“Perhaps more telling is the focus of the most recently published major folklore textbook, The Dynamics of Folklore. Whereas earlier textbooks gave little attention to women and their folklore, this book devotes many pages to women folk performers”. So the author refers to The Dynamics of Folklore in order to show that women folk performers have started getting attention, making option (d) the right answer.