Interpreting the Seismograms Below are the seismograms that arrived at three different seismograph stations located in Helena, Montana; San Diego, California; and Dallas, Texas.

Ibelieve that the answer is (a).

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.