All of the options listed (A, B, C, and D) can contribute to famine in Africa. However, if we focus on which option might be less commonly viewed as a direct cause of famine, option C could be considered different in its context. While selling crops for more on the world market can certainly affect local food availability and prices, it does not directly relate to the physical production of food or the immediate concerns of food shortage compared to the other options.
Therefore, if you had to choose one that is not a direct cause of famine, it would be:
C. Crops can be sold for more on the world market than domestically.
This option reflects an economic choice rather than an absolute barrier to food production or availability.