It demonstrates that corruption is at the center of
totalitarian governments.
This passage does not demonstrate loyalty being rewarded, so eliminate a.
Written law does not protect against totalitarian governments, because that is exactly the problem. The rules were written down. They were just being edited by the pigs. Normally that might have been a good answer, but in the context of the book, it is not. Eliminate D.
It does not clearly demonstrate that revolution is a constant threat. It kind of mentions it, since it talks about Jones coming back, and propaganda is being used on the animals. However, B is a stronger answer, because it is clearly very corrupt.