Answer:
During the war, entire cities were reduced to desolate piles of rubble.
Step-by-step explanation:
The word “desolate” as an adjective has a negative connotation. It is often used to describe a place devoid of inhabitants or people or to talk about something that is lifeless, joyless or barren. Sentence number 3 uses this word correctly because it describes how during the war entire cities ended up being devoid of people, lifeless, with only piles of rubble.