题目

如图所示，人与重物都静止。当人向右退一步后，人与重物重新保持静止，下述说法中正确的是A、地面对人的摩擦力减小    B、地面对人的摩擦力增大C、人对地面的压力增大      D、人对地面的压力减小  答案：BC解析:绳的拉力大小不变，水平方向，竖直方向，当人向右退一步后，绳与水平方向的夹角变小，则BC正确 He is a success as a leader but he hasn't _____ in teaching. [     ]A. many experiencesB. much experienceC. an experienceD. a lot experience