HELP: I get confused with correct answer in Open Assessment

Hi All,

So there is a question from PSPO open assessment:

Which two statements explain why the definition of "Done" is important to the Product Owner?

And one of the correct answers is: It assures the Increment reviewed at the Sprint review is usable so the Product Owner may choose to release it.

I was confused by it, because as cited in The Scrum Guide: "A -Done- increment is required at the Sprint Review." 

So as I understand the Increment by its definition should be "Done". 

Can someone bring the light on this confusion, please?