What was more than 2000 miles long and was located near China's northern border?

A. Great Wall
B. The Pacific Ocean
C. The himalayan Moutains
D. The Grand Canal

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.