What is the main idea of this excerpt? A. The transportation system tilhe city proposes should be improved.
B. Citizens should vote against the proposed system.
C. Cars are better than trains.
D. Americans are less responsible than citizens from other countries.

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.