If you buy ________ MP4 player in our store, you can get a watch for ________ free.

A．a; /

B．an; the

C．an; /

D．the; the

一个圆锥形麦堆的底面周长12.56米，高1.2米，如果每立方米小麦重500千克．这堆小麦重多少吨？