The correct answer is D) Cowboys could not access enough grass and water for their cows after ranchers sectioned it off with barbed wire.
The struggle in the western frontier that the lines in the poem are most likely describing is "Cowboys could not access enough grass and water for their cows after ranchers sectioned it off with barbed wire.
Cowboys were tough men that were dedicated to the ranches activities in the midwest. They herded animals and lived an adventurous life of liberty. As they worked cattle drives, they were faced with a big problem when owners of the land used barbed wire to fence their properties. And that is what is said in the poem above.