Answer: D) Theory words.
Explanation: A category is a class or division of people or things regarded as having particular shared characteristics. From the given options, the category that best fits the words in the given list, is the corresponding to option D: Theory words, because all the words of the list have in common that they can be used to describe a theory (verified, unconfirmed, credible, etc), or are related somehow to theory making (organize, precise, etc).
