<p dir="ltr"><span><span>What’s tricky about this question is that there are two verbs in it: “completes” and “can claim.” Usually, an English sentence has only one main verb unless a coordinating conjunction, such as “and” or “or,” is used to connect two main verbs. So, the only possible structure for this question is that the blank is filled with a compound relative pronoun that serves as a noun and a relative pronoun that starts an adjective clause continuing to the word “survey” to complete the subject of this question. Then, there will be only one main verb in this question: “can claim.”</span></span></p><p><br></p><p dir="ltr"><span><span>Let’s focus on the subject of this question “_______ patron completes the survey.”</span></span></p><p dir="ltr"><span><span>Of the four choices, only (A) "</span><span>Whichever"</span><span> can serve as a compound relative pronoun, which means “any one of them that,” while “one of them” can be replaced by any noun that the relative pronoun “that” intends to modify. Here, “Whichever patron completes the survey” means “Any patron that completes the survey.” </span></span></p><p><br><span><span>(B) "</span><span>Who"</span><span> is incorrect because “who” can be used as a relative pronoun, not a compound relative pronoun. If it is filled into the blank, a noun should be added before the blank to be the antecedent of the adjective clause. Besides, the relative pronoun “who” can’t directly follow a noun. </span></span></p><p><span><span>(C) "</span><span>One"</span><span> is incorrect because if it is filled into the blank, there would be no adjective clause in this question, and two main verbs would be in the same sentence. </span></span></p><p><span><span>(D) "</span><span>Any"</span><span> is incorrect, too. If it is filled in the blank, a relative pronoun should be added after the word “patron” to start an adjective clause; otherwise, there would be two main verbs in one sentence. </span></span></p>