The correct option is
A Dwellers
Option A: A 'dweller' is 'a person who lives in a tow, city, cave, etc.' 'Dwelling' means settling, and is relevant to the given sentence, which refers to dwellers in the city: city dwellers.
Hence, it forms a complete meaningful sentence and option D is correct.
Option B: 'Dealers' refers to a person who trades in something. One cannot trade in a city. This word does not form a meaningful sentence.
Option C: 'Livers' refers to the organ in our body.
Option D: 'Man' refers to the human race. But it does not form a full meaning with 'city': 'city man' sounds vague/strange.
These words are irrelevant to the given sentence in meaning.
Hence, options B, C and D are wrong.