Do you know the man ------ a book in his hand?

with a book是介词性短语作定语修饰the man,“拿着书的男人”
如果有has,就成为一个句子了,本句中主语是you,谓语是Do...know,宾语是the man,如果再用has,这个句子中就会有两个谓语,请记住一个句子永远只有一个谓语,有两个谓语时必须使用主句从句,即本句如非要用has,应改成：Do you know the man who has a book in his hand?who has a book in his hand就是从句,定语从句,修饰the man