---Would you please take a short walk with us now?  ---____. But I’m busy at present.

A．Of course not

B．That’s all right

C．I’d like to

D．Sorry, I can't

图中的箱子是光进入箱中，然后又从箱中反射出来的光路图，按它们的光的传播规律，把适当的光学器件填入箱内。