The New World Agriculture Developed in Central Mexico Around 5500

The New World agriculture developed in central Mexico around 5500 B.C.E. Spread slowly because

A) It was difficult for crops to spread north and south because different latitudes yielded different growing seasons
B) Nearby hunting tribes resented agriculture as a threat to their traditional way of life
C) The principal crops, maize and beans, were very hard to grow
D) Insects and plant diseases were endemic