Which of these rhetorical devices is most clearly used here?

D. Ethos. It is clearly the rhetorical device.

Ethos is based on the character of who is speaking or writing. It's how a person convinces the audience that he or she is prepared to talk about a specific subject. Thus linking dependence on the author's reputation (an appeal to the authority or honesty of the person that is speaking or writing). It's a persuasive strategy.

Ethos is a greek word which means "character"; therefore, it means persuading or convincing others using the character of the persuader. It is also related to the english word "ethics".

Ethos is one of the persuasion´s modes that are devices in rhetoric that classify the speaker's appeal to the public.