The correct answer is D) his reference to every citizen’s rights.
The detail that signal Lincoln’s appeal to ethos is his reference to every citizen’s rights.
Lincoln's appeal to ethos is clear when he said: "...This country with its institutions belongs to the people who inhabit it. Whenever they shall grow weary of the existing government, they can exercise their constitutional right of amending it, or their revolutionary right to dismember or overthrow it..."
Ethos is the ethical appeal that tries to convince the audience by the credibility of the individual. The other two appeals are pathos and logos. Pathos is the emotional appeal and logos is the logical appeal.