.Seeing her mother come back, ______.

A．tears ran down her cheeks

B．her tears ran out

C．she burst into tears

D．she burst into crying

如图，一辆在平直路面上运动的车厢顶部用细线吊一质量为m的小球，细线与竖直方向成θ角处于稳定状态，则

A．车厢一定做匀加速运动

B．车厢一定做匀减速运动

C．车厢的加速度大小是gsinθ

D．车厢的加速度大小是gtanθ