题目

物体沿直线以恒定加速度运动，它的位移x与时间t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． 2s   C． 4s    D． 24s                                                                     �I have _______ my father again and again not to smoke, but I can’t ______ him.A. persuaded; advise B. advised; persuade C. suggested; persuade D. suggested; advise