Answer: The bolded words form an (C.) adjective phrase.
Step-by-step explanation: An adjective phrase is a group of two or more words that includes an adjective and modifies a noun that is usually placed before the phrase. In the sentence provided, "about Native American folklore" is an adjective phrase because it is modifying the noun "article" and providing more information about it. Moreover, it is made up of the adjective "Native American", which has been used to premodify the noun "folklore".