Ethos is the rhetoric word used here.
Option (a);
EXPLANATION:
Rhetoric device is a technique of speaking in which one tries to persuade others by their speech. This is done in many ways: Ethos, Pathos, and Logos. Ethos is used to convince the audience of the author's credibility.
The above statement in the question states that the author's argument is supported by the Data received from the United States Environmental Protection Agency and suggests him to believe as a credential person. Thus, it is an Ethos that gives the exact meaning of the above statement.
