Answer:
B. In that twelve-mile stretch of living green, singing birds, flowing water and untarnished canyon walls
Explanation:
The author is being accused of exaggeration. He clarifies that it is not the case: "For those who may think I exaggerate the contrast between the former river canyon and the present man-made impoundment," and then starts describing everything how he can. Being the phrase chosen as an answer the best example of description used to support an argument.
