The rapacious plunderers did not spare even the people living in the slums.

The correct answer is C. avaricious.

Avaricious means greedy or excessively desirous of wealth or possessions. In the context of the question, the rapacious plunderers are described as not sparing even the people living in the slums. This suggests that they are motivated by greed and are willing to take whatever they can get, regardless of the consequences.

The other options are incorrect because they do not accurately describe the rapacious plunderers. Warlike means inclined or eager to fight. Barbarous means cruel or savage. Nomadic means wandering from place to place with no fixed home.