Answer:
The answer to your question is D.
Step-by-step explanation:
In the sentence above, the prepositional phrase "in the book" functions as an adjective because it is describing the location of the pictures. In order to determine whether a prepositional phrase acts as an adjective or not, you should find the object of the preposition, ask yourself which other word in the sentence is related to this noun or pronoun by the preposition and also question what kind of speech is that word? If said word is a noun, then the prepositional phrase is acting as an adjective. In this case, the NP object of the PP is "the book". This NP is related to the NP "the pictures". Therefore, the object is related to another noun phrase, making the PP act as an adjective.