Concept:The correct phrasal verb depends on the intended meaning of searching for information in a reference book.Explanation:The phrasal verb look up means to search for specific information, such as a word or a fact, in a dictionary, encyclopedia, or thesaurus.Look for means to search for something physically or generally, but it is less precise for using a reference source.Look in and look at do not fit the context of consulting a reference material.Therefore, the best choice for finding information in a reference source is look up.Answer:D. Look up