<p>In exchange for the right to accept tax-exempt donations, charities are <b>prohibited</b> from actively supporting political candidates or working in coordination on candidates' behalf.</p>
<p>The correct answer is (B) <b>prohibited</b>.</p>
<p>In this sentence, the verb form "are" is used to indicate the present tense and passive voice. The subject "charities" is the recipient of the action. The verb form "prohibited" is the past participle of the verb "prohibit," which is used to show that the action of prohibiting has been completed in the past. The past participle form is used in passive voice constructions.</p>
<p>Options (A) "prohibit," (C) "to prohibit," and (D) "has prohibited" are incorrect because they do not match the verb form required by the sentence structure. Option (A) "prohibit" is the base form of the verb, but the sentence requires the past participle form. Option (C) "to prohibit" is an infinitive form and does not match the verb form used in the sentence. Option (D) "has prohibited" is the present perfect tense and does not match the present tense used in the sentence.</p>