I don't know .What book should I buy for my son.(合并为一句)

I don't know .What book should I buy for my son.(合并为一句)
I don't know .What book should I buy for my son.(合并为一句)

I don't know .What book should I buy for my son.(合并为一句)
I don't know【 what book to buy 】for my son
请在客户端右上角评价点“满意”即可,

I don't know what book I should buy for my son.

I don't know what to buy for my son.