我不知道我该买什么书给我儿子用英文怎么说两种形式表达出来

I don't know what book I should buy for my son .
I don't know what book to buy for my son.
祝学习进步，天天进步！满意请采纳！有问题追问！谢谢！：）本回答被网友采纳