Answer:
betrayal.
Step-by-step explanation:
The word 'treachery' is derived from Old French word 'trechier' which means 'to cheat.' So, the word 'treachery' means 'to cheat' or 'to betray.'
The given phrase is taken from the novel titled 'Animal Farm' written by George Orwell. The novel is a fable that contemplates the events of the Russian Revolution, 1917.
The phrase is stating that the animals at the farm did not know which was more shocking to them, the betrayal of animals or the retribution they witnessed.
So, the close meaning of treachery is betrayal.