（本题供教学进度未超前的考生做）如图所示，光滑水平地面上静止一个内表面光滑的凹糟A，小球B由A的一端由静止释放，下列说法错误的是                                                （   ）

A．小球B一定能上升到另一侧的等高点

B．小球B运动到最低点时，凹糟A的速度为零

C．当小球B上升到另一侧最高点时，A、B速度一定为零

D．运动过程中，凹糟A在水平地面上做往复运动

Man: Thank you for your helpful assistance. Otherwise, I'd surely have missed it. The place is so out of the way.Woman: It was a pleasure meeting you. Good-bye.Question: Why does the man thank the woman

A．She promised to help the man.

B．She came a long way to meet the man.

C．She took the man to where he wanted to go.

D．She suggested a way out of the difficulty for the man.