Answer:
B). Magazines.
Step-by-step explanation:
The given sentence carries three prepositional phrases 'for his notes', 'among the magazines', and 'between the books' where the phrase consists of a preposition(in the beginning like for, among, and between) followed by the object of preposition(notes, magazines, and books) and modifier of the object(his, and the). As per the question, the object of the preposition 'among' would be 'magazines' as it exemplifies a noun that follows the preposition in order to complete the meaning of the phrase(prepositional) as well as the sentence. Thus, option B is the correct answer.