What does orwell mean when he writes about the decline of language?

He said that the issues of vague writing is described as been decayed, which is major factor that lead to the collapse in the society.

Explanation:

Orwell says that the decline of language was self-perpetuating.

He states that it is easier to think with poor English language  because it is on  decline, and as the language declines, Thoughts that are foolish becomes even easier, simpler, reinforcing the original cause.  he says its the same thing as regards to what is happening to the English language.

He also described the problem of vague writing as decay and slovenliness that has lead to decline of languages and can lead to general collapse in the society.

given the fact that the question is about the detail that best support the idea that oppressive leaders use   propaganda to achieve thir goals,   the first option does not refer to any kind of propaganda, since it only tells about that the milk and the windfall apple should be reserved for the pigs. in the second option, that is, "snowball and napoleon sent out flights of pigeons whose instructions were to mingle with the animals on the neighbouring farms, tell them the story of the rebellion, and teach them the tune of "beasts of england". it can be identified that the oppressors make use of the propaganda, which is represented by the pigeons, and the information they have to tell other animals about what was happening in the farm in order to get their objectives. for that reason, the right answer is the second option, taking into account that the third option do not refer to propaganda since it only talks about that they did not want jones back. and, finally, the last option refers to the result of the given news, but it does not mean about the propaganda they used to achieve their goals.

the characters are fiction but they are based off of people that were reaky in that situation