The Main Center(s)of Agriculture in MexAmerica Are Located Where

The main center(s) of agriculture in MexAmerica are located where?

A) Near the Rio Grande in the eastern portion of MexAmerica and the Arizona portion of the Colorado River,in the western part of the region
B) In the southern part of the region where it is warm enough to grow frost intolerant crops Students may not think "b" is a viable answers unless center(s) is referenced in the question.
C) In the northern part of the region where there is more regular precipitation
D) Agriculture is widespread throughout MexAmerica because of the region's rich soils