— _____ 

— Let me have a look. Beijing roast duck is ￥ 40.00, and the hot dog is ￥3.00. [ ]

A. May I have the bill?

B. Can I ask you some questions?

C. Can I help you?

D. Can I give you money?

一根长为L、质量为m的长木料平放在水平桌面上，木料与桌面间的摩擦系数是μ，用水平恒力F将它加速度推出桌面，当达到图中所示位置时，桌面对它的支持力的大小是______，对它的摩擦力的大小是______．