题目如右图,一个直径为1的小圆沿着直径为2的大圆内壁的逆时针方向滚动,M和N是小圆的一条固定直径的两个端点.那么,当小圆这样滚过大圆内壁的一周,点M、N在大圆内所绘出的图形大致是() The title is shown on the right. A small circle with a diameter of 1 rolls counterclockwise along the inner wall of a large circle with a diameter of 2, and M and N are the two ends of a fixed diameter of the small circle. Then when the small circle rolls over the circle For the week of the inner wall, the figures drawn by the points M and N in the great circle are roughly ()