Given the task definition and input, reply with output. In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").

a man drives away from his dog, and the dog progressively got smaller in the rear view mirror. what was happening? (A) the dog was evaporating (B) the distance between them remained same (C) the distance between them was going down (D) the distance between them was going up
D