What is the tone of "Grass"?

doubtful

jubilant

dark

respectful

The tone in "Grass" By Carl Sandburg is dark because dark can be used as an adjective which can be a synonym gloomy or pessimistic, and this book is about how human life is treated in times of war, and has a dark and unforgiving tone when talking about the industrial process of war and expresses great anger about it as well.