Incorrect: Does Everyone have their book ?
Correct: Does Everyone have his or her book ?
Can someone please tell how the correct sentence is correct....isn't it breaking the S-V agreement ?
Everyone...have
Shouldn't we have Everyone....has
The sentence stated in the Strategy Guide is correct. When we have questions, often the subject and verb are in reverse order. It's helpful to change the question into a sentence to see how the subject-verb agreement works.
"Does Everyone have his or her book?" should be re-stated in a sentence as:
"Everyone does have his or her book."
The word "have" here does not function as the main verb. It is in the infinitive, with the helping verb "does." For this reason, we should not conjugate "have."
I hope that makes sense.