Answer:
Based just on geography, Thailand would be the easiest. The next easiest would be Guatemala, followed by Ethiopia and then Iceland as the most difficult.
Step-by-step explanation:
Iceland is the most difficult because of the low temperatures and little sunlight makes it hard to grow crops. It would be hard to live there year-round without modern shelter and heating systems and other factors that do not have to do with geography. Ethiopia is the next harshest because of the semi-arid conditions there and the food insecurity that people experience because of the nature of the terrain and the difficulty with growing food. Guatemala also has an arid region as part of the Central America Dry Corridor that also contributes to aridness and some difficulty assuring adequate food supply at least periodically. Thailand would be the easiest of the options because it is semi-tropical and there is abundant vegetation and food. The temperatures are more temperate than Iceland although this increases the exposure to diseases like malaria that are associated with the tropics. Diseases like malaria are also a problem in Ethiopia and Guatemala.