The correct answer is C, subject. A cannot be correct as a direct object in this sentence are 'section', and 'discoveries'. B cannot be correct as there is nothing to possess, if it said 'whose', then it would be a possessive relative pronoun, and plus, 'possessive' isn't a function, it is just a kind of pronouns. D is also incorrect, it cannot be an object of preposition because 'anyone' isn't a preposition, it is a pronoun. And since 'who reads the science section of the newspaper' is a part of the whole noun phrase starting with 'anyone', which is a subject, this has also got to be the subject.
