Ally cropping would be most useful in the situation of c) growing crops in an area with little rainfall.
Ally cropping, or agroforestry, involves planting trees alongside crops. This technique can help improve soil moisture retention, reduce erosion, and create microclimates that enhance water availability and reduce evaporation. In areas with limited rainfall, the trees can provide shade, decrease wind speed, and help maintain humidity levels, benefiting the crops grown beneath them. This practice can lead to improved sustainability and resilience in farming systems under dry conditions.