<p>More than fifty appliance manufacturers participated in the exhibition, some of <strong>whom</strong> took advantage of the opportunity to introduce next year's models.</p><p>The correct answer is (C) whom</p><div data-answer="c"><span style="font-size: 13.008px;">In this sentence, we are referring to the manufacturers who took advantage of the opportunity to introduce next year's models. The pronoun "whom" is used to refer to the object of the verb "took advantage". Therefore, the correct choice is (C) whom. </span></div><div data-answer="c"><span style="font-size: 13.008px;"><br></span></div><div data-answer="c"><span style="font-size: 13.008px;">The pronoun "who" is used as the subject of a verb, so it is not appropriate in this context.</span></div><div data-answer="c"><span style="font-size: 13.008px;">The pronoun "which" is used to refer to things, not people.</span></div><div data-answer="c"><span style="font-size: 13.008px;">The pronoun "that" is used to refer to both people and things, but in this case, "whom" is more appropriate because it specifically refers to the object of the verb "took advantage".</span><br></div>