题目

The first robots were invented in the 1920s. Robots have appeared in Hollywood such as Robocop and the Terminator. The robots in these films are stronger, faster and more intelligent than people. In real life, robots are mainly used in factories. They do many different jobs. Usually these jobs are too dangerous, difficult or boring for humans. Robots also help disabled people and people who cannot look after themselves. For example, scientists are making a robot to help blind people. Nowadays many blind people have a dog to help them. This dog is called a guide dog. In the future, gu质量为1kg的物体静止在水平面上，物体与水平面之间的动摩擦因数为0.2。现对物体施加一个大小变化、方向不变的水平力F，下列图示中，物体在3 t0时间内发生的位移最大的是    （   ）