Stalin is using Ethos. In using quotes from Lenin, Stalin was building "credibility or trustworthiness." Wanting to convince an audience, the use of Ethos shows expertise and confidence. Quoting other great works or leaders may express experience and knowledge.
The answer to your question then is C, Ethos.
A three line stanza is known as a<span> tercet.</span>
B. She refuses to let him pity himself
