As the picture shows, it is a successful work of "shooting first and then shooting" in sports photography. In the photographer's eyes, a clear athlete is still, while a blurred background is moving.

Because the athletes and photographers move at the same speed, the reporter still takes the athletes as the frame of reference, so the photos of the athletes are very clear. However, because the background is moving relative to the athletes and the background is moving relative to the camera, the shooting background is blurred. Therefore, the frame of reference chosen by the photographer in the "post-shooting method" is the athlete, so C is correct.

So choose C.