Sprint backlog clarification

So, I have been reading and taking sample exam questions from Scrum Guide, Scrum Training Manual, Scrum Reference Card.

Scrum Guide says that sprint backlog can change. "The Sprint Backlog is a plan with enough detail that changes in progress can be understood in the Daily Scrum. The Development Team modifies the Sprint Backlog throughout the Sprint, and the Sprint Backlog emerges during the Sprint. "

Scrum Training Manual says that "The Sprint Backlog is frozen after the Sprint Planning and the Development eam will focus on delivering an Increment of “Done” based on this plan."

And then there is this sample question in Scrum training manual
"A Product Owner has the authority to replace an item in the Sprint Backlog. "

which was supposed to be false with this reason:
"The Sprint Backlog is frozen after the Sprint Planning. "

and then let's add this explanation as well to this question from scrum training manual
Q: A CEO asks the Development Team to add a new item to the Sprint. What should t
he Development do in response
A: Refer to Product owner because.....
"Sprint Backlog should not change during a Sprint on the one hand, and no one is allowed to set the priority of Product Backlog items except for the Product Owner"

And now, my BIG BIG BIG BIG question...
Can sprint backlog really change during sprint?

This question ("A Product Owner has the authority to replace an item in the Sprint Backlog. ") I THINK should have the explanation that it is FALSE because product owner doesn't own and has no authority over Sprint Backlog. Am I right?

Can anybody help my clarify and give a lengthy discussion about Sprint Backlog? Or point me to more Sprint Backlog reading materials?

Thank you In Advance

-A.V.