Correct option is D
The correct answer is: (d), Level of agriculture productivity
Whittlesey divided the agricultural systems of the world into 5 basic functional forms of agriculture.
1. The crop livestock combination
2. Methods and techniques used to grow crops and raise livestock
3. Disposal of agriculture products or livestock
4. Intensity of application to the land of labor
5. Ensemble of structures used to house facilitate the faring operations.