有些时候,多参考一下权威辞典是有好处的.下面是格林斯辞典对shall的一个解释:
You use shall,usually with `‘you',when you are telling someone that they will be able to do or have something they want.
(shall通常和you连用表示你正在告诉某人他将会做成某事或者得到他想要的东西)
这道题目MP3显然是something the son want,所以父亲用you shall这个结构来强调.