题目

—How often do you chat with your friends online?—________ I'm busy with my study.A．Only one month.          B．About twice a month.C．Almost every day.       D．Maybe in two weeks. 答案：B唐代大诗人李白的“飞流直下三千尺，疑是银河落九天”，描述了庐山瀑布的美景，被传为千古佳话。如果三尺为1米，水下落的过程中不计空气阻力，则水落到地面的速度约为（设初速度为零，g取10m/s2）（     ） A．100m/s          B．140m/s           C．200m/s          D．2000m/s