题目

Middle-class parents, who shout at their teenage children, are increasing their risk of depression and troubled behavior. Even if parents enjoy a close relationship with their son and daughter, harsh verbal discipline (严厉的口头惩戒) was found to have a bad impact on their teens’ emotional development. This form of discipline can vary from yelling and shouting at a child, to swearing and using words to shame them. Scientists looked at 976 families in the US, most of which were middle-class. During the experiment, teens and their parents completed surveys over a two-year perio研究物体运动时常用“频闪摄影”的方法，即在暗室中采用闪光灯每隔相等的时间闪亮一次，底片就记录下此时物体运动的位置．如图是两个质量相同的小球甲、乙树枝下落的频闪照片，据此记录，两球均从位置a下落到b处时，________球用时较短________球的速度基本保持不变．若两球均只受到重力和阻力作用，则________球所受阻力较大（选填“甲”或“乙”）