Well, you did not give us what the speaker talks about, so i will explain each of them to you, and you will have to choose which one is best.
A) Ethos: The beliefs and aspirations of a culture, era, community, in it's beliefs and what they look forward too.
B) Logos: Logos means reasoning, and it is used to express one's own opinion on a matter
C) pathos: Pathos means sadness, and it helps evoke pity
D) syllogism: A Logic supported by two other premises, the predicate of the conclusion, and the subject of the conclusion
hope this helps