What three assumptions were the basis of von Thünen's theory?

A. Proximity to other cities, variety in land characteristics, various modes of transportation available
B. Isolation from other cities, economic stability, homogenous land characteristics
C. Isolation from other cities, temperate climate, various modes of transportation
D. Proximity to other cities, tropical climate, variety of land characteristics
E. Isolation from other cities, homogenous land characteristics, limited methods of transportation