The claim that is not defensible is the world would be better off if political boundaries didn't exist.
In general defensible means able to be protected from attack or able to be supported by the argument.
The claim that is not defensible is the world would be better off if political boundaries didn't exist.
Therefore, D is the correct option.
Learn more about defensible here:
https://brainly.com/question/13994252
#SPJ1