题目

物体沿直线作匀变速运动, 它的位移与时间的关系是x = 24t －6t2, (x的单位是m, t的单位是s)，则它的速度为零的时刻是 A．s          B．4s           C．2s           D．24s 答案：CWhen I called Mr. Li, he and his wife ________ in the rain. A．trapped　　                           B．were traped C．were trapped　                        D．were trapping