<p><span style="">The correct answer is </span><strong style="">(C) cover</strong><span style="">.</span><br></p>
<p>In the noun clause "the fees for the three-day conference ____ accommodation, reference materials, and meals', the subject is "fees" and it is plural. Therefore, we need to use a verb form that agrees with the subject. The verb form "cover" is the correct choice because it is the base form of the verb and it agrees with the plural subject "fees".</p>
<p>The other options are incorrect because they do not agree with the subject "fees".</p>
<p>(A) "to cover" is incorrect because the infinitive form of the verb does not agree with the plural subject "fees".</p>
<p>(B) "is covered" is incorrect because it uses the singular verb form "is" which does not agree with the plural subject "fees".</p>
<p>(D) "are covered" is incorrect because it uses the plural verb form "are" which is unnecessary since the subject "fees" already indicates plurality.</p>