Answer:
C) Ethos, an appeal based on the speaker's character.
Step-by-step explanation:
Ethos is exemplified as one of the three 'artistic modes of persuasion'(as said by Aristotle), the other two being logos and pathos. Ethos implies to appeal ethically to convince the audience to believe in the idea proposed by the speaker. Such appeal is constructed on the premises of the author's reliability and command.
As per the question, the given excerpt from the speech "War Message to Congress" by President Wilson employs 'ethos' which implies an appeal that is based on the speaker's character and credibility as the speaker accentuates his authority by saying 'I am taking and of the grave responsibilities' and 'I deem my constitutional duty'. Thus, option C 'ethos' is the correct answer.