The correct answer is "Ethos". Aristotle's identified three "modes for persuasion :Ethos, Logos, Pathos which are often used in a speech.
Ethos, is the audience´s impression of you, your credibility. Stalin refers positively to Lenin and then repeats one of Lenin's famous quotes to build credibility. Thus, he aimed at convincing the audience by using a notable political figure by implying that he was as trustworthy as Lenin.