The correct option is D those
A relative pronoun functions as a pronoun as well as a conjunction. It refers to a noun that is common between two sentences and combines those sentences as one. The noun is thus, the antecedent, the relative pronoun relates it to the rest of the sentence. In some cases, the antecedent can be omitted, if it's not a specific term and is implied by the sentence. In the given sentence, the antecedent has been omitted, 'whom' is the relative pronoun that refers to it. So, the expanded sentence would be 'Whom the people prefer, those will be elected as ministers'. From the options, 'those' is the implied antecedent as it's a pronoun for a number of people who will be elected, and 'whom' relates it to the rest of the sentence. Hence option C is correct. 'He' and 'she' are both pronouns used for a single person, whereas the noun 'ministers' implies more than one person, hence options A and B are incorrect. 'Whom' is a relative pronoun that relates to the antecedent, it can't be the antecedent itself hence option D is incorrect.