I am not sure I understand your multiple choices for answers, but the correct words to put into your sentence are: 'explains', and 'is'. Because the word 'either' has been used, that changes the the word after lantern from multiple to singular.
<span>Truman set up Loyalty Review Board to investigate over 3 million. Congress set up HUAC to look for Communists. Hollywood created list of 500 people and refused to hire people on black list.</span>
