题目

阅读理解   I’m a middle school student from America. I live far away from my school. So I often go to school by bus. It takes me about twenty minutes from my home to school.    But at my school and other schools in our town, there is a “ Walk to School Day”. It is on Wednesday every week. On that day, parents send their kids to a bus stop. There are many bus stops in our town. At each bus stop, two adults lead us to walk to school together.    “Walk to School Day” stops us taking cars or buses. That is good for the air and we can get exercise too. On the way to schoo右图是甲、乙两物体做直线运动的v－t图象．下列表述正确的是        (　　)A．甲做匀加速直线运动B．乙做匀加速直线运动C．甲和乙的加速度方向相同D．甲的加速度比乙的小