题目

Ann，a mother of 3 children, is a warm-hearted social worker and she has done a lot to help people  56   The family’s dinner conversation often turns to local poor families, and she   57        tries her best to seek (寻求)help for them. This year, Ann   58   that Santa Claus (圣诞老人)would pay a special   59     to a young unemployed(失业的) mother named Ashley, who was   60    two sons by herself. One Sunday morning, the family were joyfully having breakfast    61     the phone rang, saying that the help she had requested for Ashley had 用高速频闪照相机拍摄正在做直线运动的甲、乙两小球，得到一张频闪照片，如图9所示。已知每次曝光的时间间隔为0.1s。比较甲球通过AB段路程与乙球通过CD段路程的过程中，运动较快的小球为________。