Final answer:
Option C, new, higher-yield crops, is the factor that does not cause famines, as it is associated with increased food production. The other options listed are known causes of famine due to insufficient food production or distribution challenges.
Step-by-step explanation:
The question identifies factors that can cause famines and asks which option is not a likely cause. When reviewing the options provided, the answer is C) new, higher-yield crops. This option stands out because higher-yield crops typically contribute to an increase in food production, which can help prevent famine rather than cause it. The other options presented: A) the failure of food production to keep pace with population growth, B) distribution problems caused by political turmoil, and D) crop failure brought on by sustained drought, are all well-documented factors that can lead to famine. These issues were seen during events like China's Great Leap Forward and contribute to food insecurity when governments and agencies fail to effectively distribute food even when there is a sufficient quantity produced.