(A) "changes over the last twenty years" → "over" is used for periods of time spanning duration.
(B) "fallen on evil days" → This is an idiomatic expression meaning to experience misfortune or hard times.
(C) "flung itself upon its tormentor" → "upon" indicates aggressive movement toward someone/something.
(D) "fear at the thought" → "at" is the standard preposition used with "thought" to indicate the cause of an emotion.
Hence, Option 4: (A) - (II), (B) - (IV), (C) - (I), (D) - (III) → Each preposition creates grammatically correct and idiomatic expressions with their respective sentences → correct