In paragraph 2, why does the author mention the bet that Edward Muybridge tried to settle about whether "the four feet of a galloping horse ever simultaneously left the ground"? A. To introduce and explain a fundamental principle of motion-picture photography B. To demonstrate that still photographs produced a visual effect that surpassed that of hand-drawn pictures C. To emphasize that photographers had to be willing to take risks in order to portray their subjects D. To suggest the difficulty of trying to capture animal movement in motion-picture photography