如图，小物体m与圆盘保持相对静止，随盘一起做匀速圆周运动，关于物体的受力情况，下列说法错误的是（   ）

    It was Sunday yesterday. The weather was fine. It was sunny and there were no clouds in the sky. Sandy and Sue got up early in the morning. Now they were in the park. It is a big park and it's so beautiful. They saw many people there. Some boys played football on the grass. Some girls danced under the tree. An old man walked beside the lake. A young woman and her little son looked at the fish in the lake. How happy they are!

为了提高行政效率，加强中央集权，唐太宗在国家政治体制方面完善了（   ）