题目

Five or six years ago, I attended a lecture on the science of attention. A professor who conducts research over in the medical school was talking about attention blindness, the basic feature of the human brain that, when we concentrate on one task, causes us to miss just about everything else. Because we can’t see what we can’t see, our lecturer was determined to catch us in the act. He had us watch a video of six people tossing (投掷) basketballs back and forth, three in white shirts and three in black, and our task was to keep track only of the tosses among the people in white.用黑白两种颜色的正方形纸片，按黑色纸片数逐渐加1的规律拼成一列图案：请问第个图案中有白色纸片的张数为A．B．C．D．